Slllll’ MANllfll FOREWORD This shop manual describes the maintenance, inspection and adjustment procedures of the HONDA C8750 and CB750F. The manual is divided into various func- tional groups to simplify the use of the manual. The pages for the respective groups are indexed on this pages for com venience. Each of the groups are Iurther divided into section 1. Description, 2. Specifications. 3 Diagnosis. 4, Disassembly, 5. Inspection and 6 Reassembly. Many photographs and illustrations are used to make the operations easy to understand Following are the initial serial numbers of each model at the time of change C8750 Frame No 1000001~ CB750K1 Frame No. 1055004~ CB750K2 Frame No. 2000001~ CB750K3 Frame No, 2200001~ CB750K4 Frame No. 2341915~ CB750K5 Frame No. 2525947~ CB750F(F1) Frame No. 1000001~ CB750K6 Frame No 2540001~ CB750K7 ('77) Frame No. 2700002~ HONDA MOTOR CO., LTD Service Publications Office ALL INFORMATION, ILLUSTRATIONS, DIREG TIONS AND SPECIFICATIONS INCLUDED IN THIS PUBLICATION ARE BASED ON THE LATBT PRODUCT INFORMATION AVAILABLE AT THE TIME OF APPROVAL FOR PRINTING. EMA MOTOR CO" LTD. RESERVES THE RIGHT TO MAKE CHANGES AT ANY TIME WITHOUT NOTICE AND WITHOUT INCURRING ANY OBLIGATIW WHATEVER. NO PART OF THIS PURLICATION MAY BE REPRO- DUCED WITHOUT WRITTEN PERMISSION. I4. 15. 16 17 18. 19. 20. 21. 22. 23. 24. 25. GROUP INDEX . GENERAL INFORMATION. 1~15 ENGINE REMOVAL AND INSTALLATION .......... l7~19 ENGINE MECHANICA ..21~55 CLUTCH ............. .57~61 TRANSMISSION. . 63~70 FUEL SYSTEM.. .71~82 . IGNITION SYSTEM .83~92 . CHARGING SYSTEM.. 93~102 STARTING SYSTEM . 103~108 BATTERY ........... . 109~ll4 STEERING AND FRON SUSPENSION ............. 115~122 . REAR SUSPENSION ...... 123~128 WHEELS, TIRES AND FINAL DRIVE ........... 129~139 BRAKES ............. 141~I49 BODY, OIL TANK, AIR CLEANER AND EXHAUST SYSTEM ................ 151~156 BODY ELECTRICAL AND INSTRUMENTS .157~170 WIRING DIAGRAM ..... 17l~172 ENGINE TUNE-UP. , ,137~174 PERIODICAL MAINTENANCE .......... 175~188 SUPPLEMENT T0 CB750K1~K4 ............. 189~220 SUPPLEMENT T0 CB750K5 ............. , 221~224 SUPPLEMENT T0 CB750F ................. 225~248 SUPPLEMENT T0 CB750 K6 (‘76) ............. 249~252 SUPPLEMENT T0 CB750 K7 (’77) ............ 253~264 SUPPLEMENT T0 CB 750 F (’77) .............. 265~273 CONTENTS 1-1 SERIAL NUMBER . ,. , . . ,. . . ,,,,,,,,,,, . 1 172 KEY SYSTEM i 173 TECHNICAL DATA . i a. Dimensional draw-ng l b. Specifications. . ,. . 9 Driving performance. . . ,. . .. 1~4 THREAD SIZE 1-5 SERVICE TOOLS. . . .. . 1-1 SERIAL NUMBER Fig.1»1 @ Frame serial number fig. 172 (1) Engine serial number The frame serial number is stamped on the left side of the steering head pipe and engine serial number is located on the top of the crankcase left side. Whenever ordering replacement parts or making inquiries concerning the particular motorcycle, always included the frame or the engine number whichever is applicable. (Fig. 1-1, 2) 2 l. GENERAL INFORMATION 1—2 KEY SYSTEM The key is used to operate both the main ignition switch and the handle locks Four keys are provided for each motorcycle, two are to be given to the user and the remaining two are to be kept in custody of the dealer from whom the motorycle is pur- chased so that they can be supplied as a spare , to the user when they are lost. A rubber “L14 (D Lock nut ' cap is provided to cover the head of the key ® Main ignition switch which is in use. The same code number is ®Coup|er stamped on the key and ignition switch When the key is lost refer to the switch code In case all spare keys are waste, the main ignition switch and the handle lock (key, main ignition switch and handle lock are sold in sets) must be replaced in set 3. Replacement of main ignition switch 1. Loosen the main ignition switch lock nut and remove the swnch from the switch bracket. (Fig. 173) 2, Disconnect the main swnch couplerr 3. Install the new SWItch on the switch bracket and positively connect the coupler. b. Replacement of handle lock rig.14 ® Lack spring 7 1. Remove the handle lock case mounting (2) Handle lock screw With a cross point screw driver and (9 Key remove the lock case 2. Insert the key into the handle lock and turn counter clockwise approximately 60" and then the handle lock can be removed from the steering stemr (Fig. 1—4) 3. Install the new handle lock in the reverse order of removal procedure described above. Do not forget to assemble the handle lock spring. Ciel GENERAL DESCRIPTION 25 Trouble Poor engine Probable C Valve Mechanism Black exhaust ‘ Rich fuel mixture smoke $2in do}; not return 1 liefective return spring ‘ 2. Unhook return spring auses idling 1. Improper valve tappet clearance Adjust to standard value, (Refer to page 36~37). 2. low or lack of compression Repair. pressure 3. [X(esslve valve guide clearance Replace valve and guide. Loss of power 1. Valve sticking open Replace 2. Poor valve sealing ‘ Regrind valve (Refer to page 34). 3. Weak or broken valve spring l Replace (Refer to page 34~35l 4. Improper valve timing Check valve timing and adjust if necessary (Refer to page 36~37 S. Defective (jlinder head gasket Replace (Refer to page 35). 6. \\’orn cylinder and piston Replace (Refer to page 38). ‘ 7. Worn, weak or broken piston Replace (Refer to page 38~39). ‘ ring 8. loose spark plug Relighten, Over healing 1, Heavy carbon deposit on com- Remove carbon (Refer to page 35 bustion chamber and piston head and 38). 2. Lean fuel Mixture Adjust the carburetor. 3. Retarded ignition timing Adjust ignition timing (Refer to page 83~84). 4. low Oll level, poor quality Add good grade Oll 5. Extended operation in low gear 3“" “f0 1. Poor sealing of the inlet valve ‘ Check the valve seating 2. Improper valve timing Adjust (Refer to page 36~37). 3. Improper ignition timing Adjust (Refer to page 83~84). 4 Excessively large spark plug gap Adjust the gap to 0.024~0.028in. ‘ (0 6~0.7 mm). 5. Inadequate fuel supply VVVlfite exhausti 71 Excesshmiwear of cylinder and Replace tilieipiston (Refer to page smoke l piston ‘ 38). Z. Overfilled engine oil j Adjust the oil level. 3. Excessively high Oll pressure 4. Poor quality Oll Replace with good quality oil. iAdju’st the carburetor (Refer t; page 70~7‘l), Replace Hook return spring Kick starter ‘ 1. Worn kick stater gear does not rotate 1 p;wl Replace 173 TECHNICAL DATA 1—3 TECHNICAL DATA a. Dimensional drawing 0 ‘rgm emu ‘ 15 62>va 19 moo: Q m £9 a \D N R l\ 35'. .n 1! ‘ (“mos riw‘SEJOIG 885(34 B) (I mom Fig. 1-5 L GENERAL INFORMATION . b. Specifications CB 750 Item angliep . Metric Overall Length 55.0in, 2,160mm Overall Widlh “Jill. ‘ 885 mm Overall Height 45.5lll. i 1,155 mm 5 Wheel Base i 5min, 7i 1.455 mm 2 Seat Height 31.5 in. ii 300mm E FOO! Peg Height 121m. ‘ 3‘01“"! Ground Clearanee 55in. 1 160mm Curb Weight 517.3“). ‘7 235 kg Weight Distribution [/2 2711/2095». ; 123/205 kg 7 Type 7 7 Dongle EEaTe’qun. steel r. Suspension, Travel 7 7 "73.15.. fork:;avel Shinf 143 In": 77* R. Suspension, Travel 7 "if Swlgiirm, 7 7 "Miami as trimifi \7 r. Tire Size, Type 7 {25-19 14 mitt-b we, 7 e airierssur27270kig/cm’,;psi R re si£e7ype iii 770015 (4 PR) Blockr me, 7 tire air pressure inks/{ma is psli g ‘r. Blake, Lining Area 7 DISC brake, 7 7 V Ilnjlgr area 71.9in’x72f19cm1x77 E R. Brake, Llning Area intern; exanping no; Iming areailZIn’; 53 an; Fuel Capacity Fuel Reserve Capacity Caster Angle Trail lenglhi rrpnr rat on Capatiiy 74.71151; 3.9lmp.gal i W ism. 1.31.1.5 gal. 111ml”: 7 SIT W 3.74 ills 7 ’ 95 0;!“ V i 7 7 7.0-7301577 V i £20430“. 7 7 Type Air-cooled, +stroke, one engine Cyllnder Arrangement 7 7 7 7 Leylinder in lme '7 Bore and Stroke 2.401x2JWinf 7 61x63 mm Dlsplacement 44.93 cu in. ”i 736 cc Compression Ratio 90 Carburelor, Venturi Dia Four, piston valve, 25mm dia, Valve Train Cnain dvive overhead camshaft ENGINE Maximum Horsepower 67 EMF/3M1] rpm Maximum Torque 44.12 lellUm rpm 6.1 Rpm/LG!) rpm Oil Capaciry Oil Tank Capacity 7.39 US. pm, 6.16 Imp. m. 3.5 iii. 42 us. pl., 155 Imp. pt. 2 lit. lubrication System reused pressure and dry sump Air Filtlaiion Paper element 1-3 TECHNICAL DATE Item English 1 Metric Valve Tapper Clezrance IN: 0.(X)2, EX: 0.003inr IN: 0.05, EX: 0.08am! DRIVE TRAIN Engine weight (include oil) 17am), 80kg Ail Screw Opening 131/8 Idle Speed 9mrpm Clutch Wet, mum—plate Tlansmission Primary Reduction, Secondary Reduction 5»speed, constant mesh Plimary. 170a, Secondary: 1357 Geav Ratio | 2.500 ,, II 1708 u lll 1.333 N [V 1.097 » V 0939 Flrlal Reducion Gear Shift Pattern 1667, drive sprocket 151, driven sprocket an [alt toot return type Battery Capacny Ignition Starling System Altermlor Spark plug Battery and ignition coll Electrical motor and kick pedal Three phase AC 12 V-OJZ kW/5,m0 rpm 12 V—‘M‘AH NGK D»B ES 6 1. GENERAL INFORMATION CB 750 K 1 Item Emma l Merrie Overall length asuiri. ‘ 2,160mm Overall width 34.5 in. 885mm Overall height 44.5in. 1,155 mm E wheei base 57.3 in. i 1,455 mm E seat height 31.5in. | worrini A Foot peg height 12.2in. ‘ 310mm Ground clearance 5.5m, l 140mm Dry weight 479m. A ziairg Type Double cradle r. suspension, travei Telescopic Iork, travel 56 "1.76433; ‘ R. suspension, travel Swmg arrri travel am (as mrni 7 r. tire size, pressure R. tire size, pressure r. brake lining area R. brake, Fume 325» 19 (4PR) Rib pattern, (Ire air pressuve 401—18 (4m Block pattern tire air pressure ZORg/cm‘ lze psi) rig szep! area sassq. in (3829am’) internal expanding shoe lining swept 332so in (2m5cm‘) 2.0kg/cm’ iza psl) Trail ieugth Fronx fork oil cipacfly Front tarlt oil capacity lining area ruei capacity 7 A n 4.5.us gal 3.7lirip gal 7 77m, _7 Fuel reserve capacity 7 nus gal. 11 imp. gal. ‘77 7 7 7 5m ‘Caster angle 7 _ 63" ‘ W - » 7W 7 35min 220-230“ (to till it dry; Toefiazito tili airer Arzining) 6.9-7.1 015 Air cooled, 4 slroke o.i-l.c, engine Type Cylinder arrangement i 4 cylmder In line Hare and stroke 2.402x2.4eoiri. ‘ 5x630 min Displacement 44.90pm. 736cc Compression ratio 9.0 1 Valve train Chain driven over head cart-shalt 'E Oil capacity 3.7 U.S.ql. 3.1Impiql. 15h! ,5 Lubrication system Forced pressure and dry sump c linder head ' Ypressure compresw" 12 kg/cm‘ (17013150 l Open At 5° (before lop dead center) Intake valve l Close Al 30* latter bottom dead center) Open Al 35° lbetore bottom dead center) Exhaust valve Close At 5" (after top dead center) Valve tappet clearance IN: 0.1112, EX: 410mm. IN: 0.05, EX: 0113mm Idle Speed 950lmp Cnbnntor 1—3 TECHNICAL DATE Item Englilh Metric Type Piston valve Selling mark 7A Main jet 3120 Slow jet 3 40 Air screw opening 1:3/8 turns rloat height flBGGirL 16mm Clutch Wet multi plate type Transmission 5-speed constant mesh Drive train Electric-l Primary reduction 1.703 Gear film l 2500 Gear ratio ll 1.703 Gear ratio III 1333 Gear ratio VI 1.097 Gear ratio v 1.939 Final reduction 2,567, drlv! sprocket 15 T, drlven sprocket «it Fear shirt pattern left foot operated return system ignition Battery and ignition coil Starting system Slaltlng motor or kick starter Alternator Battery capacity Three phase AE. generator 1i V/0.21kW/S,G)Orpm 12 V44 AH Spark plug ch DBES»I., NDX Z4FS Headlight Low/high lEV—towlsow Tail/stoplight Tail/stop 11V—7/23W (SEA TRADE No. 1157) Turn signalllght Front/rear lz v.23/23w Speedometer light 12 v-3w Tachometer light 12 v.3w Neutral indicator light 12 v—sw Turn signal indicator light 12 veaw High bean indicator light 12 vezw I. GENERAL INFORMATION CB 750 K2, K3, K4 min Engliala l Metric Ovemll lengrli aseiii. 2,175 mm Overall Wldlh 34.3ln. 370 mm Overall height 4min. 1,170rriiii é Wheelbase s73iii. 1,4ssrrirri E Seal height 31.9iri. 810mm 5 Fool peg height 12.2in. 310mm Ground clearance 5.5 iii. 140 mm Dry weigh: 479 lb. l 21Bkg Type Double cudle r. suspension, iravel Telescopic fork, navel 56in. (143 min) ll. suspension, travel siiiriiig arm, travel 33in, (as mm) r. lire sire, pressure 3.25.19 (4 m Rib panerri, [Ire air pressure 2.0 kg/cm“ (2)) psi) R. tire slle, pressure _ 4.00.13 44 m Block pallem, rire air pressure 2.0kg/cm’ (25 psi) 0 r. brake, llning area Dlsk brake, Ilmng swepr area sense in. (332.9 :m’) E R. brake, lining area lnlemal expandlng shoe, llnlng swepx 342mm. (2205 cm') h Fuel capaciiy 7 V 4—.su,s.gal, 3.7lrnp. g; l 17‘!" Fuel reserve capaclly i nus gal. 1.1linp. gal 7 5m Casier angle 7 ' 6y Trail lunglh W 3.7 in. .7 W i 95 rnin rrpnr lork oil capacity 75-73 DIS 7 ‘ 22mm cc lro lill il dry) Front fork pil capacity 53—54025 77155460 cc (Elm aner draining) Type Air cooled, 4 stroke 0.H.C. engine Cylinder auangement 4 cylinder in line acre and snake 1402le in. 610x63.0mm Displacemem 44.9cu.in 716 (c Compression rario 9.0 1 Valve train chain driven over head camshafl _3 Oil capacity 3.7U.S qr, lumps“, 3.5m E lubrication system forced pressure and dry sump W 12 kg/cm‘ (170.7 psi) '""k' "'“e 3:: if sis; :5:L‘:’:;::.“*:;‘.;:"::I’... Exhaust valve Open At 35° lbelore bollom dezd center) Close M 5° (alter top dead cenlel) Valve rapper elearance IN: 0.002, EX: 0.0mm. IN: 0.05, EX: 0.08mm ldle speed 950mm Electric-l 173 TECHNICAL DATE Item ' Bulb]: \ Metric Type a Piston valve _ Setting mark 7A ‘E Main let mo "(313105) E. Slow jel HO 0 Air screw opening 1:315 turns mm height ‘ 0.86“". 26 mm Clutch Wet mnlti plate lype Transmission fl sspeed conslanl mesh Primary reduction 11706 a Gear ratio i 2.500 3 Gear ratio II 11703 .3 Gear ratio III 1.333 5 Gear ratio VI 1.097 Gear ratio v 1.939 Final reduction Gear shin pattern Ignition i Starling system Alternator 21667, drive spiockel 18 T, driven sprocket 48 T left foot operated return system Battery and Ignition coil Starling motor or luck starter lhree phase kc. generzlor 1211/7021 kW/smo rpm Hattery capacity 12 V-‘H AH Spark plug Nix Dezé—L, NDX 1425 Headlight low/high lzv—aoW/sow Tail/stoplight .,, Tail/slop 12V~3/32 cask TRADE Nov 1157) Turn signauight From/rear u v.3mch (SAE TRADE No. R1034] non) Speedometer light 12v~2 cp (SA! TRADE No. 57) recnometer Ilghl 12 V»: C? (SAE nun: No. 57) Neutral indicator light 12v~2cp (SAE TRADE No, 57) Turn signal indicator Iigh' 1ZV>1CP (5A5 TRADE N0. 57) High beam indicator light 12v-zcr (SAE TRADE No. 57) Position Ugh! 11V—4CP (SAE TRADE No. “) IO 1. GENERAL INFORMATION 6. Driving Performance Curve (One Rider) s 10X IO 6‘ ENGINE SPEED (RPM) 25 50 75 100 50 100 150 DRIVING SPEED Driving Performance Curve (Two Rider) 10I 16< 1 t \S‘ 50% 2nd 3rd win 4th .7 h, I filo “e m ._ 5 4th \, QM» ENGINE SPEDIRPM) 441 (200) 330 220 100 DRIVING FORCE LBS(KGI 125 (MPH) 200 (KPH) 441 (200) 5th on u: o RCE LBSIKG) 220 8 100g DRIVI 25 50 70 100 125 MPH) l—lé—l 50 100 150 20 DRIVING SPEED Fig. 1—6 0 (KPH) l—A THREAD SIZE 1 l 1—4 THREAD SIZE All threaded parts used on the HONDA CB 750 conform to ISO Standard (International Standardization Organization). The differences between the dimensions of the JIS (Japan industrial Standard) bolts, which were previously used, and the ISO bolts are in the thread pitch, width across flat and the thickness of the head. Do not use any JIS thread to fit [SO thread, otherwise the thread will be damaged. The width across flat IS also different from JIS standard except 6mm bolt or nut, thus the wrenches are not common to the ones based on “5 standard except 10 mm. The table below lists these dimensions for the [50 standard bolts. Pitch Nominal dia. Width across flat as. 177 Unit : mm Nominal Width across flat Pltch dia ' ISO JIS ‘ iso iis‘” 3 ‘ 5.5 . 6 0.5 06 I 4 7 ‘ a l 0.7 0.75 5 8 9 08 0.9 6 10 (Same as JIS std.) 10 1.0 (Same as JIS std.) ‘ 1.0 a 12 14 1.25 (Same as JIS std.) i 1.25 10 14 17 i 1.25 (Same as JIS std.) ‘ 125 12 ‘ 17 19 1.25 1.5 14 19 21 15 (Same as JIS std.) ‘ 1.5 16 ‘ 22 23 15 (Same as JIS std.) 1.5 ‘18 . 24 26 15 (Same as JIS std) 1.5 20 1 27 29 ‘ 15 (Same as JIS std.) 1.5 To make it possible to identify the ISO threads, they are marked as shown below. Hex. bolt Cross screw @7Semi—spherical embossment Nut E— Semi-spherical dimple fig. H 12 GENERAL INFORMATION 1-5 SERVICE TOOLS (:3 0M C) @ m O 0D @ Ref‘ No‘ ‘ TOOL No. ] DESCRIPTION 07900—30UXXX) Special Tool Set for CB 750 ® o7m30001oo Inlet/Exhaust valve seat cutter 90" ® 07580-5680400 Inlet valve seat top cutter ® 079805510400 Exhaust valve seat top cutter ® 07980—5510500 Inlet valve seat interior cutter © o79w551osoo Exhaust valve seat interior cutter © 0798175510000 Valve seat cutter holder ® o7ms11ww Valve guide reamer 07957—32900!” Valve spring compressor ® 079424000000 Valve guide driving & removing tool ® 07908—323m Valve tappet lock nut wrench ® 079424000200 Valve guide driver ® D7906—323()0(X] Heat bolt 12 mm wrench F5 SERVICE TOOLS 13 (1'3 ® Refr No. TOOL NJ.“ 7‘ DESCRIPTION ® 079545000000 Piston ring compressor (2 pcs) ® 079587300000) Piston base (2 pcs) ® 07933—3(I)OOOO AC enerator rotor puller ® 07909—3rmooo Spar plug wrench ® 0792273000000 Drive 5 rocker holder ® 079167283w00 Clutch ock nut wrench ® 07945731me Counter shaft bearing removing tool @ 07945—3m500 Counter shaft bearing removing tool ® 07915—2160CDO 1 Stem nul box wrench ® 07902—2000000 \ Steering stem top thread wrench H I. GENERAL INFORMATION Ref. No. l TOOL Nol DESCRIPTION ® 07967—300000!) Front fork assembling bar ® 07959~329m Rear cushion disassembling & assembling tool ® 07914—32300” Master cylinder circlip pliers ® 0791773000000 Hollow set wrench @ 0794973000000 Bearing driver handle ® 07946-3m0100 Front wheel bearing driver @ 079464000200 Pear wheel bearing driver ® 079454300CIX10 Final drive shaft bearing driver ® 07401—0010000 Carburetor float level gauge ® 07999—3000000 Crankshaft turning handle @ 07910—3230101 Retainer wrench ® 07910—2330000 Retainer wrench ® 07947—329CKXX) Oil seal guide 175 SERVICE TOOLS GAUGES AND ATTACHMENT Ref. No‘ ‘ @©@©®®® TOOL No. 07506—3000m0 075104000000 075106003100 07510—3000“ 075044000100 07504—303020) 079754000001 ‘ DESCRIPTioN OII pressure gauge (10kg) Oil pressure gauge adaptor Vacuum gauge attachment (A) (2pcs) Vacuum gauge attachment (B) (2 pcs) Vacuum gauge set (4pcs) Vacuum gauge (1pcs) Joint tool set ummmumumIu...”mmunuu.-...Im..mm,m......w...........m w... ,,-.m.m..,....,m ENGINE REMOVAL AND INSTALLATION GROUP CONTENTS 2-1 DESCRIPTION ........ 2-2 ENGINE REMOVAL . . 2.3 ENGINE INSTALLATION. .19 2—1 DESCRIPTION The engine is made as single-unit including clutch and transmisSIon and mounted to the frame with four mounting bolts. The single-unit engine may be dismounted by disconnecting wiring system, fuel system, exhaust system, air intake system and final drive system, and remowng engine mounting bolts. However, the following parts can be disassembled from the engine without dis- mounting the engine from the frame Clutch assembly, a.c. generator, cam chain tensioner, gear shift arm, gear shift drum stopper, gear shift positive stopper, contact breaker assembly and carburetor. 2-2 ENGINE REMOVAL 1. Shut off the fuel tank valveand disconnect the fuel tubes from the fuel tank valve. Raise the seat and remove the fuel tank. (refer to page 82). 2. Remove the oil filter and drain the engine oil by removing both the on tank drain plug (refer to Fig. 1577 on page 154) and the engine oil drain plug. (fig. 271) 3. Remove the exhaust mufflers. 4. Disconnect the tachometer cable at the cylinder head cover and remove the high tension cord caps from the spark plugs. (Fig. 272) 5. After removing the throttle valves from the respective carburetor, detach the car- buretors from the inlet pipes. 6. Remove the air cleaner case. 7. Remove the kick starter pedal and the ' clutch cover. Fig. 2-2 G) Tachometer cable 13 2. ENGINE REMOVAL AND INSTALLATION 8. Disconnect the clutch cable from the . clutch lever. (Fig. 2—3) 9. Disconnect the stop switch spring and remove the brake pedal and the step bar. 10. Disconnect the two engine oil hoses at the engine and remove the oil tank. Dis- connect the oil tank breather pipe from the ., -~\_ » - upper crankcase. (Fig. 2-4) ri5.273 Q) Clutch lever (2) Clutch cablc 11. Remove the gear change pedal and the dnve chain cover and disconnect the drive chain, After disconnecting the chain, the both ends together with a piece of wire to prevent chain from coiling, 12. Disconnect the starter motor cable, dy- namo lead connector and the stop switch lead wrre. (Fig. 2-5) Note : Disconnect the starter motor cable at the magnetic switch and disconnect the negative terminal of the battery to . prevent accidental shorting. 13. Unscrew the engine hanger bolts and nuts, (Fig. 2-6) 14. Raise the rear of the engine and remove lt from the right Slde. fig. 275 ® Starter motor cable % Dynamo leads connector Stop switch lead LEFT SIDE VIEW RIGHT SIDE VIEW . / Fig. 2—5 10mm bolt @ Rear engine hanger lower bolt @ 8mm><56 bolt . Engine hanger bolt A @ Engine hanger bolt c @ Ernrnx45 bolt 273 ENGINE INSTALLATION 19 2—3 ENGINE INSTALLATION ‘I. Mount the engine from the right side and position it in the proper location. 2. Install the hanger bolts and nuts and ex» ercise care that the ground cable terminal is installed together with the engine rear upper bolt (Fig. 2-7). The hanger plate and the stop switch stay are also mounted with the hanger bolts. 3. Connect all the wirings and cables. 4. Connect the drive chain, install the drive chain cover and the gear change pedal. 5. Mount the oil tank, Install the Oil hoses and connect the oil hoses to the engine. Note: When connecling the oil hoses, make sure that the oil deliverly hose and the scavenge hoses are not any crossed. 6. Install the rear brake pedal and connect the stop swrtch spring (fig. 278) 7. Connect the clutch cable to the clutch lever. 8. Install the clutch pedal and the clutch cover. 9. Mount the carburetors and install the air cleaner case. 10. Connect the throttle valves, the high tension cord caps and the tachometer cable. 11. Observe the Installation of the N05. 1 and 2, and Nos. 3 and 4 mufller bands Install the exhaust mufflers. (Fig. 279) 12. Mount the fuel tank and connect the fuel tubes. 13. Add engine oil into the oil tank (refer to page 178) rig.2 9 \n Exhaust muffler band GROUP 3 ENGINE MECHANICAL mmummmuiu...uimuuiumumiuumimmi”umi...uuanm....u...,.u.m.. my ”4.. M. ‘ i..y.uiumumiHumiHmuiu.um..mum...m.. CONTENTS 3—1 GENERAL DESCRIPTION. DESCRIPTION . . . . SPECIFICAI’IONS . DIAGNOSIS . t 3—2 LUBRICATION SYSTEM a. Description . . .. b. Disassembly I c. Inspection . t. d. Reassembly . 3-3 CAMSHAFT DRIVE . a. Description , b. Disassembly . ct Inspection H d. Reassembly , 3—4 CYLINDER HEAD. a. Description ‘ b. Disassembly I c. Inspection I, d. Reassembly p 3-5 PISION AND CYLINDER ........ a. Description . b. Disassembly . c. Inspection d. Reassembly . 3—6 CRANKSHAFT AND CONNECTING ROD . a. Description ............................. b. Disassembly . c. Inspection d. Reassembly . 3—7 PRIMARY DRIVE. 3. Description . b. Disassembly . c. Inspection d. Reassembly . 3—6 KICK STARTER .. a. Description . b. Disassembly c. Inspection. :1. Reassembly ....................... .. 55 22 3. ENGINE MECHANICAL 3-1 GENERAL DESCRIPTION DESCRIPTION HONDA CB 750 is a 736 cc, 4ecycle, inline engine incorporating an overhead cam, and mounting 4 carburetors. rials-1 lell Slde View H544 nghl side vrew SPECIFICATIONS . Type ‘ onc. arr—cooled, 4—eycle Cyllnder arrangement 1 4 cylinders in line sore and stroke \ 2.401X2,480m, (61x63 mm) Dlsplacemem ‘ 44.93 cu-inv (736 m m Compression ralm ! gig-1 Compressian pressure ‘ 170 lbs/m1 (12 kg/cm’) Valve rlrning lnlex valve: open n,r,D.c. 5° . InIel valve: close AVB.D,C. 30" Exhaust valve: open B.B.D,C, 35° Exhausl valve: close AIDE. 5- lgniiion timing B.T.Dic. 6' at wool-pm, 40‘ at 1,500 rpm . 3-! GENERAL DESCRIPTION 23 nem Standard value Sevvlceable lam on pump Body inslde dvamelH 10,65~:(I)62§ 13;" 135%; :51 Rotor dlameler 2052:2110? 2",“ l 145:2: 3}" Ram: Ihlckness ldellvevy sldel 03%;:2gg'g7m'; ‘ 017703; :én Ratov lhlckness (scavenge s-de) ”flgz‘mém; 0:173: ‘rgln Body depth (dehvery side) ‘ 01730333273211; ‘ 017513; 2}“ Body new. (scavenge Slde) l 033;:22‘331: I 01427.3; :m i , , fl , ; , , 7 i Leak stopper valve dlameler 0353:9722“; 01770;} :5 Leak stopper body Innev drameler 0,1332%; ',,',‘m ‘ (13573;; :m Rellei valve drametev l $332233}: If,“ 0:163: gm Rellel valve body mner dlameler ‘ $:;;;:2;gg‘m':1 0142733 :m Cnmlhafl I _ . Shall (enter drameler 3333:3323 12m 01815;: :m i 08637~06646 .n, 08623 W Shah end dlameler 2‘939~219wmm 2159 mm | 1016~1 103 In 10996 In Base crrcle 27 ”N230; mm 2793 mm Cam lln (mlet) ‘ “ifégfafizsifl, 0371;; 'nnlm Cam llft (exhausl) “7923:9364; 027933;le Cum-m holder Camshaft beanng dnameler 0333:3533? LS," 0383' }n Rotker arm beanng dlameler i 014173;:2iéfl 1:,“ 01273? :5. Rocker arm shaft drameler 21%;:‘3'1‘33 12;“ 014178155. ,7 , , , , fli WWW, , , ‘ , W ,, , Cylinder held l Valve guide mner dlameler “25322303‘2 021$. Clearé'nce belwee’n’va’IVe’gliide \ 770.000“? film-y", ’ b.0032an ' andiyalve s|em (IN) l 7 0.01:0.03 mm fl one mmii C|earance between valve and: ouols~om24m 00039m. ’ 5 ma valve ”$16117 004~006rnm 7 7 VOJTVm 7 Valve sprlng Free length (ouler) 1465 2". 151043 'rrrl‘én Free length (Irma!) 135:2 2:... “357633;“ . " 2402~24624.n. 2741) in. Cyhm‘lcl bore ‘1‘ 015.6102 mm l 61.1 mm Pislon diameter 3&5“; 52);" ‘ 26309;; :5“ Piston pm bore diameter 2333:2353 :3" I 015:3; :5, Pismn pin diameter gzsvmgml‘l’fifi'r: ‘ 31532 13;» 2‘ 3. ENGINE MECHANICAL ltem l srandara value Serviceable limit Pm” “"3 om16~onozn m. 0-0071 "1- Ring side clearance (mp) 0.044107 nun 015mm ' 0.0065 in. Ring side clearance (second) fijflfififlfi; 0,165 mm .0004 . 1 . 00055 in. Ring side clearance (all) 09010333: 0.14mm om~omsrn ocoozarn. End gap (rap and second) 015.0,: mm 07 mm . o.ooo4~a 0012 in. 00025 in. End gap (on) o1~o.3 mm 0.7 mm Cnnk-lnft‘ 1 4168~14173inv 1.415 an. Journal diameter 35.39.4600,“, 35,94mm c r 14168~1.4‘l73ln. 1415In. Crank pm dlameler 3599~35wmm 3594mm . omwmfim odojlrn. shah to hearing clearance 001~0.046mm one mm | Connectlng roll 03912,.0'5919 m 05933 m. small and diameter 151016451034 mm 15 07 mm "oooe~ . V 2 . Bearing oil clearance °'ooz~g*$;8,,',’,‘n 00318612," Large and diameter Select an, refer lo page 41~44 Select m, refer to page ”~44. Number or men. of kick ” 7' #. starter gear _ __ ,Eim 7—.“ k, 7 —— chk flute: en ' 07866~0789in owe-n, Inner diameter 1998~20041mm 7211075 mm Shah outer diameter 3’33332‘1’9’3322; 01793;; Ifi'm DIA NOSIS Trouble Probable Causes Remedy Engine does Valve Mechanism not Sta" 1. Excessive by worn piston ring Replace. and cylinder 2. Seized valve Replace. 3. Seized piston ’ Replace. 4. Valve timing out of adjustment 5. Low or lack of compression pressure - Pressure leak 5. Delective cylinder head gasket 6. Warped gasketting suriace of the cylinder and cylinder head ‘ Adjust, (Refer to page 31~32). r Grind the valve to obtain good valve seating or replace. Replace, Repair or replace. 3. ENGINE MECHANICAL 26 ”A ,n: cam—waw ZO—HAAVHMm—DA Nxm KUFJE 1:0 3. ENGINE MECHANICAL 27 a. Description The engine is adry sump type incorporating a separate oil tank which is mounted on the right side of the frame. The oil in the tank is delivered under pressure by the oil pump to lubricate the engine components. The Oil accumulated tn the crankcase sump is returned to the oil tank by the scavenge pump, however, part of the all is deverted to lubricate transmission components 1. Oil pump The oil pump is a rotor type trochoid pump mounted on the bottom of the crank» case and driven from the primary shaft through the kick gear. It consists of both the delivery and scavenge pumps, a leak stopper valve and a relief valve (Fig. 34) (Oil leak stopper valve) During engine operatlon, the Oil pressure opens the Oil leak stopper valve to malntaln orl flow, and when the engine stops, the valve closes to prevent flow from the oil tank. (Fig. 375) (Relief valve) Relief valve is set at a specified pressure so that whenever the oil pressure exceeds thls pressure, the valve opens and bypasses the 0|] to crankcase sump. In thls way, the constant on pressure vs maintained. This valve l5 incorporated In the delivery side of the oil pump. (Fig. 3~6) Standard valve setting ls 56.9le ammo; 0.2kg/cm2) at 4,000rpm engine speed at oil temperature of 176°F (80°C). 2 Oil filter Oil illter IS a full flow type using a re- placeable element fllter. All the oil from the Oil pump passes rig.a4 5) Dellvery pump @ Suvenge pump @ Leak stopper valve @ Relief valve rig.” L on leak slopper sprlng a, on leak stopper valve rig.” tr Rellcl valve :2 Rellel valve spring rigs—7 @ Crankcase Q) on filter case ® Oil filter element ® By-pass valve spring (9 By-pass valve 5) Center bolt 23 372 LUBRICATlON SYSTEM By-pass valve swig By-pass valve Fig. 3-9 ti) Oil filter center boll @ oil filter case fig. 3710 @ oil pump ® on pump mounting bolts through the filter to be purified before being senttothecrankshaft. Filterassembly is mounted at the front of the engine with a bolt. Further, a by-pass valve is incorpo- rated in the bolt to prevent Otl stoppage when the element becomes clogged. (Fig. 377) (By-pass valve) When the element becomes clogged and the oil pump discharge pressure rises exces- sively, the by-pass valve open and the Oll Will by-pass the filter element and flow directly into the main gallery. At 21.3:2.3|bs/in.z (1.5:02 kg’cml) pressure difference, the valve is functioned. (Fig. 3-8) 3 Oil pressure warning lamp The red orl pressure warning lamp is located to the lelt Side of the tachometer on the gauge Normally the light will be on when the engine lS stopped and the main key swrtch is turned on. However, it Will go oh as soon as the engine is started and Oil pressure reaches 7,1lbs‘iina (0.5 kg cm ) If the warning light came on while riding the engine should be stopped and the cause of the problem determined When operating the engine under extre- mely high orl temperature (over 244°F, 100’0, the warning light may intermittently come on at idling speed (800~900rpm), however, this does not indicate a problem. 4. Drive chain lubrication The drive chain is automatically lubricated by the chain oiler equipped on the drive shaft. The oil which is soaked into the felt oil reserve element located at the end of the drilled passage in the final drive shaft leaks out along the face of the drive sprocket by the centrifugal force to lubricate the chain. b. Disassembly The Oil pump can be removed With the engine mounted on the frame, 1. Unscrew the oil filter center bolt from the front of the engine and take out the oil filter case. (Fig. 379) 2. Remove the oil pan from the lower crank- case to get access to the oil pump. 3. Unscrew the three oil pump mounting bolts and remove the oil pump. (Fig. 3—10) 3 EmlNE MECHANICAL 29 4. To remove the oil pump rotors, dis- assemble the side cover and remove the rotor A, (delivery side); next, remove the dowel pin and pull out the shatt from the rotor body. This will permit the rotor B (scavenge side) to be removed. (Fig. 3~11) 5. Remove the metal oil screen and unscrew the four bolts at the pump base to remove the oil pump body. (Fig. 3712) 6. For disassembling the oil leak stopper valve, remove the oil leak stopper cap bolts. The oil leak stopper cap, spring and oil leak stopper valve can be removed from the oil pump. (Fig. 3—13) 7. For disassembling the relief valve, un- screw the relief spring cap, the relief valve spring and relief valve can be removed. (Fig. 343) c. Inspection 1. Check the oil pump Slde cover for cracks, 2. Outer rotor and body clearance Measure the clearance between the outer rotor and the body with a thickness gauge. lf the clearance between rotor and body is greater than 0.0138 in. (0.35 mm), the rotor or the body should be replaced, depending on which part is worn. (Fig. 3414) 3. Measuring the tip clearance Measure the clearance between the outer rotor and the inner rotor With a thickness gauge and if it is greater than 0.0138 in. (0.35 mm), the rotors should be replaced in set. (Fig. 3‘15) Outer rotor lnner rotor Fig. 3—15 8 @ Thickness gauge l Mctm‘ ml screen '2. 6mm hex bolts .34 on pump base in on pump body Fig. 343 ’i Leak stopper valve ’2‘ Rellef valve @ Pump body Fi 3—1; Thickness gauge 3. g Outer rotor 30 3—2 lUBRlCATION SYSTEM 4. Measuringtheleakstoppervalveclearance Measure the body inside diameter and the leak stopper valve outside diameter using a dial gauge or a micrometer and if the clearance is calculated to be greater than 0.0067 in. (0.17 mm), the leak stopper valve or body whichever is worn beyond serviceable limit should be replaced. 5. Measuring the relief valve clearance Measure the body inside diameter and the relief valve diameter usinga dial gauge or - . a micrometer and if the clearance is greater “Er 3’16 0" 51W"?! than 0.0039 in. (0.1 mm), the body or the valve whichever is beyond serviceable limit should be replaced. 6. Measuring the rotor thickness and the body clearance Measure the rotor thickness with a micrometer and the depth using the depth micrometer and if the clearance is greater than 0.0047 in. (0.12 mm), the parts should be repaired or replaced. 7. Cleaning oil strainer Wash the oil strainer in clean solvent. Be sure to replace the oil strainer with a new one if damaged. (Fig. 346) d. Reassembly 1. Assemble the oil pump component parts in accordance with Fig. 3-17. Assemble the relief valve, relief valve spring and screw the relief spring cap securely. 2. Assemble the oil leak stopper valve, spring, 0 ring and oil leak stopper cap, and then tighten the two bolts. 3. Mount the inner and outer rotors B into the oil pump body, and insert the oil pump drive gear. Do not forget to install the rotor dowel pin. 4. Mount the inner and outer rotors A into the pump body. 3—2 LUBRICATION SYSTEM 15x25 “0" ring il pump gasket ® on pump body @ 11x15x3 Oll seal ® Outer rotor A @ Inner rotor A :3 0|] pump lefl cover 3 6x59 flzt screw 9 6mm flat washer 43 5x32 hex boll ® Relief spring cap @ Reliel valve spring Fig. 3-17 @ Relief valve @ on pump base @ oll stlainer screen Q on leak slopper seal 93 Oil leak stopper valve @9 on leak slepper spring @ 15x25 “0" ring Oll leak slopper cap 6mm flat washer 6; 6mm hex boll 32 3. ENGINE MECHANVCAL Nole: Do nol forget to install the 0- ring on the side cover. (Fig. 3—18) 5. After completing the assembly of the rotor, turn the shaft by hand to assure that it is turning smoothly. rig, 371a ® “0" ring 6 Immerse the pump in oil and turn the pump until filled with oil before reinstalling the pump on the crankcase, (Fig. 349) 7. when reinstalling the Oil pump on the crankcase, do not forget to install the oil guide pins (3 each) and the O-ring (3 each). 8 Changing Oil and filter element proce- dures should be referred to group 19 on page 178, run-19 a) on pump assembly (2) on pump drive gear 3—3 CAMSHAFT DRIVE a. Description The camshaft is supported at the four points by two aluminum alloy camshaft holders and driven by an endless chain off the timing sprocket located at the center of the crankshaft. The cam chain is guided by an amustable cam chain tensioner, a guide roller and a cam chain guide. (Fig. 3720) b. Disassembly 1. Unscrew the three 6mm cross screws and remove the breather cover. (Fig. 3421) 2. Loosen the 6mm cross screws and remove the cylinder head cover. find-21 ® Breather cover Fig. 3—22 ® Cylinder head cover (3) Cross screws 373 CAMSHAFT DRlVE 33 Q) Camshah @ Clulth @ Camcham a) Ki(k 5mm spindle © Camcham tens-oner (9 Final driven shalt @ Crankshaft @ Mamshm @ Primary chain ® Countershafl © Pvimary dnven sprockel @ AC generator Fig. 3.20 3. Turn the crankshaft lo allgn me timing index line (on the tachometer gear end) so that it is parallel with the cylinder head mating surface (with the key groove Ioward [be top) .and then remove the camshaft holder cap. (Fig. 3723) “5.3.23 (3 Camshaft ® Timing indu marked linu 34 3. ENGINE MECHANICAL 4, Detach the cam chain tensioner holder from the cylinderl (Fig. 3724) 5. Unscrew the two cam sprocket mounting bolts and then loosen the valve tappet adjusting screws Unscrew the four rocker arm shaft mounting bolts and pull out the rocker arm shaft using the rocker arm shaft remover (Tool No 0703030001) being careful not to damage the holder. (fig. 3»25) .. w Ea : Note: Rocker arm No. 1 and No. 3,..md Fig.3724 G) Cam Chain tenstoner holder ”Ck" No. 2 and N°' 4 '"e_ ‘dem'ul’ therefore, lag the respective rocker arms for idenlificalion. .4. c _ ' —25 (D Rocker arm shaft mounting bolts @ Rocker arm shalt remover 6, Remove the cam chain from the cam sprocket and then pull out the camshaft from the camshaft holder at the left Side (Fig. 3726). 7. Detach the camshaft holder from the cylinder head. rig. 3-25 @ Camshaft sprocket @ Cam 8. Remove the sixteen cylinder head mount- ing nuts, the five 6 mm mounting bolts and then separate the cylinder head from the cylinder. Use a special tool (Tool No. 079067 3230000) to loosen the 6mm mounting bolts on both SldSS. Loosening sequence of the mounting nuts IS performed in the reverse sequence Indicated Fig. 3733 on page 67. (Fig. 3727) 9. Remove the cylinder from the crankcase. Fig. 3-17 Removing cylinder head mounting nuts and bolts 3'3 CAMSHAFT DRIVE 35 10. Remove the two cam chain tensioner mounting rubbers from the crankcase and then remove the cam chain tensioner roller assemblyc (Fig. 5728) 11. Cam chain guide roller can be removed from the cam chain tensioner by pushing the cam chain roller pin. 12. Remove the cam chain guide pin from the bottom of the cylinder and remove the cam chain guide from the cylinder. (Fig. 3'29) c. Inspection 1. Measuring the camshaft clearance (Perform the measurement with a micro- meter and inside dial gauge) a, Assemble the camshaft holder on the cylinder head and assemble the cap on the camshaft holder making sure that the cap and holder are stamped with the identical markings. Torque to 6.0~B.0 it. lbs (80~110 kgvcm) bl Measure the bearing inside diameter ”1 both the vertical and horizontal direction using the inside dial gauge and calculate the average value. Next, measure the camshaft bearing with a micrometer and then compute the shalt clearance. If the clearance is greater than ooosainl (0.11 mm), the camshaft holder and the cap should be replaced in set. Further, the clearance may be measured using a press gauge, (rig. 5430, 31) 2. Measuring the cam lilt The camshaft lift is checked by measuring the height of the camshalt lrom the bottom of base Circle. If the total height for the inlet cam is less than 1.411 in. (35.36 mm), and for the exhaust, 14392 in. (35.36mmt the camshaft should be replaced. Further, it the base circle is less than 1.099 in. (27.93 mm), the camshalt should also be replaced. (Fig. 3732) 3-32 ® Micromelel @ Cam height “5.372: r. Tenswoner roller mounting rubbers {g Cam chain tensioner Fig. 3 29 . Cam (ham guide 2‘ ram (ham guide pm fig. 341 Q Micromelel (g) Camshalt bearing «3» Cylinder 36 3. ENGle MECHANICAL 3. Checking the bend in camshaft Support both ends of the camshaft on the V blocks and check the dial gauge reading of the camshaft center support while rotat- ing the camshaft. if the run-out is greater than 0.005in. (0.1 mm) TIR, the camshaft should be replaced. (Fig. 3—33) 4. Inspect the camshaft and camshaft holder for scratches and cracks. If found defective, it should be replaced. 5, Checking cam chain guide roller ‘5-3’33 © Dia' gauge Check the chain contact surface for wear, @ Camshaft . , . and replace It, If found to be excesslve. (Fig. 334) ’27 d. Reassembly ’1 Route the cam chain through the cam chain tensioner roller, mount it on the upper crankcase and install the mounting rubbers. (Hg. 3 35) 2, Assemble the gasket, the two dowel pins (on both Side of the exhaust), two 0 rings (on Inner side of the inlet) and then install the cylinder being carelul not to damage the piston or the piston rings. The work can be facilitated by using the piston ring Compressor (Tool No. 07954-3000000) and the piston base (Tool No. 07958 3003000). (Fig. 3 36) 3. On the cylinder gasket flange, assemble the two dowel pins, two 0 rings and the cylinder gasket,and then mount the cylinder head followed by installing and torquing the mounting nuts and bolts in accordance With Fig. 3738. Torqued the nuts to 13.7~ 15.2 fI-lbs. (1.94.1 kg-m.) (Fig. H7, 38) Fig.3~34 (9 Cam (ham guidfl roller ® Cam chum tensioner “5.3446 G) “o" rlngs rig.3—37 (D “0" rings (2 Dowel pins @ Dowel pins 3-3 CAMSHAFT DRIVE 37 CB 750 K4 0 Cylinder head gasket rings On the cars Engine No. 2352923 and after, a collar and oil seal (rubber) are inserted into between the cylinder and head at the points 4, 8, 5, 9, 14,10, 11 and 7 In Fig. 338‘ Note: Install the oil seal onto the collar and insert them into the attache ins hole in the cylinder. 4. Timing the valves a. Position the Not 1 and No.4 cylinders to the top-dead-center by turning the (rank shaft and aligning the No. 1 and No A “T" marks on the spark advancer to the index mark (Fig. 3-39), During this operation, check the movement of the cam chain to make sure that it is properly “3. 3739 in Index mark fitted on the timing sprocket. ‘27 “1" “Wk b. Fit the cam sprocket on the camshaft and route the cam chain through the right side. c. Assemble the cam chain on the sprocket before mounting the cam sprocket. Place the camshaft on top of the camshaft holder and align the timing index line on the right side of the camshaft, so that it is parallel to the top surface of the camshaft holder, (The key groove must be toward the toplv in this condition the base circle of the No. 4 cam is toward the top and the No. > 1 cam is in the overlap position, (Fig. “3'34" ® Sail/'2" 3—40, 41) Index lines “T” mark ‘ 1.4 mark @@ 33 3. ENGINE MECHANICAL d. At this point, the sprocket can be mounted on the camshaft with the two sprocket mounting bolts. (Fig. 3—42) 5. Mount the rocker arm on the rocker arm shaft and install the mounting bolts. (Fig. 343) Note: Rocker arms No. 1 and No. 3, and No. 2 and No. 4 are interchangeable, therefore, do not error during instal- _ A , , , Ialion. rigul u; Cam sprotkel (2) Cam chain ‘9‘: L , » 6, Cam shalt holder and cap are matched set and can be identified by the identical numbers stamped on the holder and the cap Torque the bolts to 6.5~9.4 ft-lbs (90 ~13!) kg. cm) 7 Push in the push bar for the cam chain tensuoner Install the tensioner on the cylin- der, loosen the tensioner adjusting bolts and then retrghtcn the bolts and lock with the lock nut. (Fig. 3 44) 8 Adiust the valve tappet clearance. (Fig. 345) Refer to page 42~43. 9. Install the cylinder head (over with the Sixteen uoss straws. 10. Mount the breather cover With the three CFOSS SCTCWS ' - h (ens oner holder Fig. 345 3 Valve tappel adjusting screw m. 3 44 33 5:3: cnuarm I @ Valve Iappet lock nut ® Tensiuner adiusung bull @ Ihlckness gauge 34 CYLINDER HEAD 39 3-4 CYLINDER HEAD a. Description The engine being on overhead camshaft type, the valves are located in the combus- tion chamber in the head. The combustion chamber is semi—spherical design for greater power output and the valve guides are press-fitted into the head. Remove the valves Compress the valve springs using the valve spring compressor (Tool No 079577329003) and remove the valve cotters, springs and valve in this order. CAUTION: Compress the valve springs with care attention paid not to damage the valve stem seal. b. Disassembly 1, Remove the cylinder head in accordance with section 3-3b on page 26~29r 2, Disassemble the cylinder head using the valve remover (Tool No. 070331730001 and 0703140010) and disassemble the following parts: cotter, retainer, valve spring (both inlet and exhaust), valve stem seal, spring seat in the order. (Fig. 3—46) 34 Remove the valve guude using a valve guide removing tool (Tool No 07942_ 3000000. (Fig. 3—47) c. Inspection 1. Measuring the clearance between valve and valve guide insert the valve into the valve guide in the cylinder head and measure the clear< ance in both the X and Y axes, using a small dial gauge. (Fig. 348) If the measured clearance is greater than 0.003 in.(0.08 mm) for the inlet valve or 0.004 in. (0.1 mm) for the exhaust valve, both the valve and valve guide should be re placed. The replacement valve gunde should be one that is oversize. Use a valve guide driving tool (Tool No. 0794273000000) to drive the valve guide fully into the head.(fig. 3749) Complete the valve guide installation by reaming out the valve guide using a valve guide reamer (Tool No. 079%6110GX1) to the standard dimension. Standard inlet and exhaust valve guide inside diameter is 0.2599~D.2603 in. (6.6~6.61 mm). Fig. 346 Q) Valve llller (a Cylinder head “3.349 (9 Valve guide driving tool ® Valve guide 40 3. EmlNE MECHANICAL 2. Measuring the width of the valve seat and vertical valve run-out Place the valve on the V block and check the vertical run-out of the valve face by using a dial gauge. If the run out is greater than 0.002in. (0.05 mm), the valve should be replaced. (Fig. 350) Further, measure the width of the valve face contact and if it is greater than 0.079in (2.0mm)l the valve should be replaced However, it the valve is not seating uniformly, the valve seat should be repaired using a valve seat cutters For information on the valve seat cutting operation refer to fig. 3— 51. There are three types of valve seat cutter shown in Fig. 3-51. The valve seat interior cutter will cut the bottom or the port side of the valve seat and the valve seat top cutter will cut the top of the valve seat (combustion chamber side). Finally. a 90" seat cutter is used to cut the seat. The width of the valve seat should be finished h . to 0.03910 0.051 in. (1~1.3 mm). After the “5.3-50 (I) Dial gauge mum; of the valve seat, use a lapping f I n5. 3-51 ® Valve seat interior cutter @ Valve seat mp cuttev © Valve seat 90' cuuer compounds to lap the valve to the new seat. Apply light coating of oil to the valve stem before assembling the valve into the cylinder head: Use the installation tool (Tool N0. 0795773290000) CAUTION: Use the valve seat grinder (tool No. 0778270020000, A set) to correct the valve seat width and contact from the follow- ing serial numher. E No, CB 750 E—2242714~ Read carefully the instruction provided with the valve seat grinder. 3~4 CYLINDER HEAD 4| 3. Measuring the valve spring Measure the free height of the valve spring using a vernier caliper and make sure that it conforms with this specification listed on the next page. The spring forces are also listed the re- ference. (Fig. 3—52) 4. Measure the rocker arm shaft support area with a micrometer and measure the rocker arm shaft bearing diameter bore using inside micrometer. Calculate clearance and if it is greater than 0.0047 in. (0.11 mm), re- place either one or both of the parts. (Fig, 3—53) 5. Removing carbon from the combustion chamber. Assemble the valve into the combustlon chamber and remove the carbon using a carbon brush or a scraper, being careful not to scratch or damage the parts. 6. Measuring flatness of the cylinder head Place a straight across the mounting sur- face of the cylinder head and check the clearance with a thickness gauge at several points to make sure that the head is not warped. If the clearance between straight edge and the head mounting surface is greater than 0.009 in. (0.25mm), the head should be reworked or replaced by a new head. In any event, the warp of the head should be less than 0.002 in. (0.05 mm). (Fig. 3—54) Standard Serviceable Item value limit 593m?” Int (mm) ln. (mm) Sp'mg 0“! lnnervalve 1.50 1.4556 22.345: n; 3.52 @ Vernier caliper sprlng (3&1; (a1. 0) kg/zsmm ® spring Outer valve ”220 1.4748 45.6~5l.6 spring (41.2) (40.0} Its/28min raga—53 or Rocker arm shaft (23 Mlcrometer (a) Camshaft holder (4) Inner dlal gauge Fig. 3754 Q) Stretch ® Thickness gauge 42 3. ENGINE MECHANICAL d. Reassembly 1. Clean the component parts of the cylinder head and assemble them in accordance with Fig. 355. Q) Valve gulde © Inner valve sprlng @ Set ring @ Valve stem seal (a) Valve cotter ® Valve spring seat (9 Valve retainer (9 Exhaust valve @ Outer valve spring ® Inlet valve mass 2. Install the cylinder head in accordance with section 373d on page 36~38. 3. After assembling cylinder head, the valve tappet clearance should be performed to assure proper clearance in the following manner. a. While slowly rotating the crankshaft clockwise (see arrow) watch the lt1 cylinder inlet valve tappet. when this tappet retracts all the way and then starts to rise, watch for the alignment of the timing index mark and the “T" mark. Check the 1-4 cylinder mark. In this position the tt1 piston will be at T.D.C. (top dead center) of the com- pression stroke, and both the inlet and exhaust valves in that cylinder should be fully closed. The valve tappet clearances of the valves marked with the 0 in the table on the next page can be checked, (Fig. 3—56) 3*5 PISTON AND CYLINDER 43 jN 1JNo.2‘No.3 No.4 m ‘ D j x 1 o x EX 0 l O l x x Note: The cylinder are numbered 1~4 starting from the left side. b. Check the clearance of both valves by inserting the thickness gauge, prOVided in the tool kit, between the tappet adjusting screw and the valve stem. It clearance is correct, there will be slight drag or resistance as the gauge is inserted. If clearance is too small or large, adjustment is necessary. (Fig. 3-57) The standard valve tappet clearance is IN 0.002in (0.05 mm) EX 0.003 in (0.08rnm) c. Adjustment is made by loosening the tappet screw lock nut and turning the adjusting screw until there is a slight drag on the thickness gauge .Hold the tappet adjusting screw in this position and tighten the lock nut. Recheck the clearance With the gauge. Next, turn the crankshaft 360°, this Wi" Put NO- 4 P'Slo" ""0 the (OP‘ ’ Fig.3 57 11/ Valve tappet adjustlng screw dead-center of the compressmn stroke and (2) Valve tappct lock nut Will permit the checking of the remaining 4‘7 Thane” 33““ valve tappet clearances marked x in the table above. 4. Install the cylinder head cover and breath er cover. 375 PISTON AND CYLINDER a. Description The piston is made from selected aluminum alloy casting. This material is light and making it suitable for high speed. In addition, it pos- sess good heat conducting property to rapidly . dissipate heat. Furthermore, the coefficient “53.53 37. Piston pm clip (5; Fusion of heat expansion is small thus minimizing @ “5‘0" DI" the warpage at elevated temperature and permitting a small piston to cylinder clearance design. b. Disassembly 1. Remove the cylinder in accordince with section 34b on page 32~35, 2. Remove the piston pin clip, push out the piston pin and remove the piston from the connecting rod. (Fig. 358) Note: During the piston pin clip removal, exercise care not to drop the clip into the crankcase. 3. Remove the piston rings from the piston. 3. ENGINE MECHANICAL V c. Inspection 1, Measuring the cylinder bore, taper and out of round. (Fig. 3—59) Measure the cylinder bore at the top, center and bottom, measuring in both X and Y axes, using a cylinder gauge. If the diameter is greater than 2.406in. (61.1 mm), the cylinder should be rebored and honed. Further, if the taper and the out of round is greater than 0.0020 in. (0.05 mm), the cylinder should be repaired in same manner as above. Measure the cylinder diameter at the point of maxrmum wear, Next, select the proper oversize piston to be used (0.25 mm to1 mm oversue in increments of 0.25 mm) and determined the proper boring dimension. When boring is completed, finish up by honing. The minimum clearance between the piston and the cylinder is at the skirt section With a dimension of 0.0004~0.0016 in. (0.01~0.04 mm). - Oversize piston diameter (fig. 3—60) , Oversize Piston diameter (D) 76:57 025 611154.135 mm— ‘ 0/5 *0; Asiieswuasnr 7 03 0.75 N i ' snisifins mm 7 0/5 1.00 7 7 €1.9E:61.985 mmi 2‘ Measuring the diameter of the piston Measure the piston diameter at the skirt, 90°irom the pistonpin hole, using a micro- meter. lf the dimension is less than 2.3939 @rkMicr‘o—m-eter in. (60.85 min), it should be replaced. (Fig. (2 Piston 3’61) 3. Removing the carbon Remove the carbon from the piston top and the ring groove by using a carbon scraper. If the ring groove is damaged or exces- swely worn, the piston should be replaced. 4. Measuring the piston ring end gap (Fig. 3»62) Fit the ring into the cylinder bore and measure the gap at the end of the ring using a thickness gauge. When only the ring is to be replaced without boring the cylinder wear, the ring gap should be measured at rig." 3.51 5.3—6: (D Piston ring @ Thickness gauge the skirt of the bore. urmmmrumumrum...umimumumumu GROUP 6 FUEL SYSTEM CONTENTS 671 GENERAL DESCRIPTIONI DESCRIPTION ............. SPECIFICATIONS ,. DIAGNOSIS. 6~2 CARBURETOR Description. . t Disassembly . . Inspectionv Reassembly. 9-0.?!” 6.3 FUEL TANK AND VALVE ................................. 81 a, Description, t. ....... V81 b Disassembly . . 82 ct Inspection. . .. .52 d Reassembly .................. . ........... H. . ,52 6—1 GENERAL DESCRIPTION DESCRIPTION The two fuel tubes connected to the fuel valve supply the fuel from the fuel tank to the four carburetors, The fuel in the carburetor float chamber is sucked into the engine in the proper air- fuel mixture to conform with the engine speed. This has a great influence on the engine performance. In an engine with four independent carburetors their precise adjustment is particularly important for smooth operation The fuel valve has three positions, ON, STOP and RES; which can be selected by the lever. 72 SPECIFICATIONS 6. FUEL SVSTEM Fuel tank capacity 4.7 US gal. (18 lit) Fuel tank reserve capacity Carburetor setting (able i 105 US ptr (5 lit.) Air screw opening Type Piston valve, 4pcs, Main bore 7 717.102 in. (23 mm) Main jet 77 7 3120 Air jet is 106 7 7 * Air bleed A3177 7 7 0035 in (0.9 trim) x 4 7 7 7 7 “:7 ‘ 77 7 7 7 01035 in, (0,9 mm) x47 77 X3 3 626256. (0.6; @707sz A34 1 7 7 0.024 in (0.6 mm) x 2 Needle jet 77 6.1707216175 in, in x 3.8“ mni) Jet igéle 77 7 7 77 7 0.098 in. (2.48; 71:")77 Cutaway7 7 fi 77 7 ll 25 [fécess 0,047 mm '(‘LZ mm), 77 depth qopgin (0.2 mm)] Setting mark B750A 1 11/8 Slow jet 7 77 7 7 1:40 7 77 Valve seat 7 7 7 7 77 77 7 7 0,079 inTZ :nm) 7* Pilot outlet ‘ 0.047in. (1.2 mm) 6—I GENERAL DESCRIPTION DIAGNOSIS r Trouble Probable Causes Remedy not start 2 idling Improper running of engine Engine does 1. .0‘ N Poor engine 1, euro .Asuvur- Choke open to wide . Carburetor air screw opened too far Air leaking into the cylinder head Clogged carburetor slow jet 5. Clogged fuel valve or piping Clogged vent hole in the fuel filler cap No fuel in the tank Clogged or loose carburetor slow jet Improper lloat level Improper air screw adjustment Improper carburetor linkage operation Air leaks Jet size too small . Improper float level Clogged carburetor main jet Improper carburetor linkage operation Air leaks close choke. Adjust air screw, Retighten carburetor connecting tube. Check, clean and retighten. Disassemble and clean ‘ Disassemble and clean. Fill tank with gasoline Check, clean and retighten. Adjust (Refer to page 68). Adjust (Refer to page 71~73). Adjust ‘ Tighten all air passage connection. Replace larger size jet. Adjust. Clean and retighten, Adjust. Tighten all air passage connection, 73 74 6. FUEL SYSTEM 6—2 CARBURETOR a. Description The quadruple piston type carburetors are mounted on the cylinder head with a stay plate. Choke lever is a link type which operates all four choke valves simultaneouslyt Fig. 671 shows the construction details of the carburetor. “3.64 @ Carburetor top (a: Cable adjuster @ Jet needle ® Top washer ® Lock nut o3 Needle jet @ Flat washer [0) Cap @ Needle jet holder (9 Valve seat «9 Throttle spring @ Mam jet (a Float arm pin {3 Throttle valve @ Slow jet @ Fluat ® Needle set plate (3 Rubber cap @ Cllp As the air enters the carburetor, it passses under the throttle valve where vacuum pressure is produced due to the restriction caused by the throttle valve extending into the main air passageway. The fuel dlscharge outlet is located in this so—called venturi area so that the vacuum pressure can draw out the fuel. This carburetor incorporates both the main and slow system. - Main system The fuel passes through the main jet ® and enters the needle jet holder ® where it mixes with the bleed hole located around the needle jet holder. The fuel air mixture passes by the opening between the needle jet ® and jet needle ® and is discharged from 672 CARBURETOR 75 below the throttle valve @. lt is here that the mixture is combined with the main air and after being atomized, is taken in to the engine. . Slow system The air which enters from the inlet passes through the outside of the air screw where it is metered and enters the slow jet bleed hole. It mixes with the fuel which enters the slow jet (3 to produce a full spray that is discharged from the pilot outlet at a point under the throttle valve, This mixes with the air from the air inlet to form a combustible mixture before being taken into the engine. ~ Float chamber The carburetor must provide a proper mIX- ture of fuel at different throttle openings and engine speeds; in order to accomplish this, the fuel level in the carburetor must be maintained constant. The float chamber func- tions to serve this purpose, The fuel from the tank enters the float chamber through the fuel inlet passage, between the float valve seat GA and float valve and fills the chamber to the level where the float t5, rises to shut off the fuel by seating the float valve against the valve seat through the action of the float arm. As the fuel is consumed, the fuel level in the float chamber, drops the float will follow the level, and the fuel wrll start to enter the chamber between the opening of the float valve and valve seat to maintain a constant fuel level. (Fig. 671) b. Disassembly 1. Turn the fuel tank valve to the “STOP" position, remove the fuel lines from the fuel valve body, raise the seat and pull the rear tank rubber mounting away from the rear tank mount. Remove the fuel tank. 2. Remove the throttle valve from each of the carburetors. (Fig. 672) 3. Loosen the air cleaner connecting tube and insulator bands and remove the car- buretors as an assembly. (Fig. 673) 4. Unscrew the two 6mm screws and dis- mount the respective carburetor from the stay plate. (Fig. 674) Disconnecting the individual choke rod will separate the carburetors. 5. In order to remove the needle jet from the throttle valve, first, disconnect the throttle cable from the throttle valve, and then remove the needle set plate from the throttle valve. (Fig. 6—5) figs-3 fir Air (leaner connecting band rz- Carburetor insulator band Fig. 54 @ Carburetor 137 Setting screws @ Carburetor stay pme 5.6-5 (9 Throttle valve (3 Needle set plate © Jet needle 76 6. FUEL SYSTEM rig.” ® Float @ Main jet @ Float valve set (A) Slow jet “5.6-7 (i) Float ® float level gauge hw—m- l Fig.6—B ® Jet needle @ Float‘valve 6. Remove the float chamber retaining clip and the following carburetor components can be removed with a small screwdriver: slow jet, main jet, needle jet holder, float and float valve sett (fig. 676) c. Inspection 1. Carburetor adjustment should be made in accordance with the description on page 78~81. 2. Fuel level check Remove the float chamber and set the float arm as shown in the Fig. 6~7 so that it just barely touches the valve and in this position, check the position of the float with the gauge set vertically, At a standard setting the float should just barely come in contact with the gauge, If there is clearance between the gauge and float or if the float is interfering with the gauge, adjustment should be made, The height of float can be adjusted by bending the float arm using a narrow screwdriver. 3. let needle, float valve The jet needle is constantly moving and if It is found to be excessively worn, it should be replaced. Further, check the wear of the valve and the valve seat and if it is de- fective, part should be replaced. (Fig. 673) 4. The clogging of the respective jet should be cleaned by blowing out the jets with compressed air followed by properly torquing the jets. 6—2 CARBURETOR 77 d. Reassembly 6; Rubber cap ® Alr screw (2) Cable adjuster @ Throttle stop screw sprrng @ lock nut @ Throttle stop screw @ Cap @ 79x13 O-rlng 5, up @ T-type luel tube loint @ Top washer a Slow let ® Throttle spllng @ Needle let (g Needle set plate as Needle jet holder @ (hp 59 Mam let a let needle @ Flat washer ® Throttle valve @ Float valve set ® 1.0x10 splrt pln r3 Float a; 5mm llat washer @ Hoar arm pm (3 Choke rod a» Float (lumber washer ® Plug screw 9 5mm llal washer 43 Flat washer Ga Dram plug @ Alr screw sprlng a; Float chamber set clrp Hg, 59 1. Wash all the parts and dry completely wlth compressed air before reassembly. Assemble the main jet and slow jet on respective location. (fig. 6-10) raga 6-10 5) Main jet @ Sluw jet 75 o. FUEL SYSTEM 2. when either the float valve or valve seat requires replacement, they should be re- placed in set. (Fig. 6711) 3. Install the respective carburetor on the stay plate with two mounting screws and connect the choke rod to the carburetor; make sure that the action of the choke lever IS smooth. 4. Install the carburetor assembly on the cylinder head. 5. Assemble the throttle valves and cables on the carburetors and actuate the throttle grip to assure smooth movement of the cable. 6. Carburetor adjustment Before attempting carburetor adjustment, make sure that the following adjustments have been performed properly. a. Contact braker point gap b ignition timing c Valve tappet clearance d. Spark plug gap e Crankcase oil level Preliminarly adjustment a. To make easy of accessto the throttle screws on all carburetors, the fuel tank should be removed. b, To check the operation of the choke valves remove the air cleaner upper and lower cases. Observe the choke valves from the rear side of the carburetors whether all valves are fully closed or not, when the choke lever is operated. If there is a clearance greater than 0.02in. (0.5mm) between the choke valve and body, adjust the clearance by leng- thening or shortening the choke lever Fig.6~12 (j) Choke lever (2‘) Choke valve (1) (9 Clearance between Choke valve and body i '6'” % Lanfxmfri'k © Thmme 5”” mew adjusting rod connected to the annex carburetor. (Fig. 6-12) 0.04~D.08irl(1~2mm) c. Adjust the throttle stop screw to align the “T" mark to the index mark stamped on the carburetor body. Perform adjust- ments on all carburetors. (Fig. 6-13) d. Loosen the throttle cable adjuster lock nut and turn the cable adjuster to either directions to obtain the free play of the throttle cable outer within the range of 0.M~0.08in (1~2mm). After tightening the lock nut check the movement of the outer cable. Fig.6—14 ® Cable adjuster The four throttle cables should all be @ Cable adjuster lock not adjusted uniformly. (Fig. 6-14) 672 CARBURETOR 7 9 e. Gently turn the air screws in until they seat, then unscrew them one full turn each. (Fig. 6-15) f. lnstall the air cleaner, air cleaner upper and lower case, fuel tank and fuel lines. Fill gasoline in the fuel tank (2) Final adjustment For final adjustment use the vacuum gauge. Before attaching the vacuum gauge start the engine and warm up to operating temperature of 140~175°F (60~80°C). a. Stop the engine and remove the plug of adapter attachment hole on each car- buretor bodies. Attach the adapters of vacuum gauge to all carburetors: the long adapters 60 are for insude carburetors and the short ones for outside carburetors. Fit the vacuum gauge hose securely on the adapters. (Fig. 6‘16, 17) bl Start the engine and run it at the idling speeds Check RPM on the tachometer and if the RPM is not in the range of 850~950RPM adjust all throttle valve stop screws uniformly to obtain the proper speed. Adjustment should be done within the range of We turn in both directions while checking the vacuum gauge. c The standard vacuum pressure reading should be 20~22cmHG. in all four gauges. If any of these gauges indicates pressure higher or lower than the standard range adjust it with the throttle stop screw. Turning the stop screw clockwise will reduce the pressure and turning it counter- clockwise will bring the pressure higher. (Fig. 6-18) fig. 6-15 @ Air screw (2) Throttle stop screw fig. 6716 (r) plug Fi|.6-‘lll (1) Vacuum gauge 80 o. FUEL SYSTEM 40 ‘0 20 20 \ smug "My 0 o NORMAL THROTTLE VALVE THROTTLE VALVE EXCESSIVELY OPEN EXCESSIVELV CLOSE Fig, 649 d. it the swing of the gauge needle Is large tighten the gauge restrictor valve to reduce the needle movement within 2cmHC. When the indicated pressure Is lower than 15cmHg, check the ioiiowing possible defects. - inlet or exhaust valve sticking open - Absence of slack in the throttle cable - Loose spark plug . Loose clamp on the carburetor connecting tube e. Turn the air screw slightly at a time within 1/8 turn in both directions from the original setting, pausmg for about 5 seconds to locate a point of highest engine speed by the tachometer. Perform this adjustment to all carburetors. If it takes over a full turn more or 1/2 turn less than the original setting to change the engine speed check the following possible cause. Air screw adjustment requires over 2 turns Ala/szcrfilwnadjustment requires less than Clogged airrpassage Q9839!" “wig. Worn air screw valve Clogged slow jet passage float level too high . 'jgrloat’iével toojo'w’” ’7 : Loosened slow jet Excessively worn air screw valVe seat i. Open the throttle valve slowly about 1/4 turn by the throttle grip for 30 seconds. Observe the vacuum gauge and note the location where the drop of pressure is not even to the other carburetors Slow down the engine and adjust the throttle cable adjuster on the carburetor concerned. if drop of vacuum pressure is quicher than others turn the adjuster clockwise, namely increase the tree play of the throttle cable. if the drop of pressure is slower than the others, turn the adjuster counter clockwise. The difference of the vacuum pressure the four carburetors should be less than 2 cmHG. Tighten the lock nuts and fit the rubber caps, when the adjustment has been completed (3) Final adjustment without vacuum gauge a. Set the idling speed to 850~950 RPM with the throttle stop screws. Turn the throttle stop screws clockwise to increase the idling speed. Adjust each carburetor in the same amount. 6-3 FUEL TANK 81 b. Observe the tachometer and listen to the exhaust noise and/or place a hand at the exhaust outlet to check the exhaust pressure. Turning out or in very slowly the air screw, obtain the highest engine idle speed or the highest exhaust pressure. Repeat the same method on all carburetors. The adjustment should not be done exceeding 1/8 turn in both directions. If there is no change in the engine condition even the adjustment exceeds 1/2 turn in both directions, check possible cause of the defects according to the items in section (2) e. Adjust the idling speed again by the throttle stop screws to set back to the standard RPM. c. Slowly twist the throttle grip 1/4 turn to open the throttle valve and allow seconds to run Listen to the exhaust noise and if the noise for four cylinders are not identical and random difference as the throttle opened, an adjustments |S necessary. Place a hand at the exhaust outlet and check the exhaust pressure of all four cylinders. Locate one or two carburetors of which the exhaust pressures are different from the others. Adjust them with the throttle cable adjusters. Turning the adjuster clockwise will increase the throttle cable and play and reduce the exhaust pressure. Turn the adjuster counterclockwise to increase the pressure. After completing the adjustment, tighten the adjuster lock nut and properly install the rubber seal cap. (4) Other inspections. a. Snap the throttle grip several times and then recheck the vacuum pressure readings or exhaust noise to assure that they are all the same. b. Turn the steering all the way to the right and left side and snap the throttle grip few times to check that the carburetors are operated smoothly. c. The air vent tube must be positioned over the air cleaner case. d. The adjustments of the throttle grip free play and the grip damping force should be referred to the group 19 (page 182) 6—3 FUEL TANK AND VALVE a. Description The fuel tank is mounted on the frame body directly above the engine and is installed on the frame body through the fuel tank rubber cushions. (Fig. 6—20) Fig.6") ® Fuel tank front cushions @ ruel tank @ Fuel tank rear cushion 32 6. FUEL SYSTEM b. Disassembly 1. SWItch the fuel valve to “STOP” and disconnect the fuel tube from the fuel valve. (Fig. 6721) 9“ 2, Raise the seat, open the fuel tank rear cushlon and remove the fuel tank to the rear and raise. 3. Remove the fuel strainer cap, 0 ring and fuel strainer screen. 4. Remove the two fuel valve mounting screws and remove the fuel valve from the tank. (fig. 6722) c. Inspection 1. Inspect the fuel for leaks. 2. Inspect for clogging of the filler cap vent hole. 3. Inspect the front and rear cushion rub- bers for deterloration, wear and other damages. ‘ 4 Inspect for damage to the valve cock l packlng and the filter screen, and then clean Hg. 5:12 'E‘r‘u—J‘mfifi them with gasoline. (Fig 6-23) ® Fuel valve mounhns “mm 5. Inspect the fuel tube for defects, d. Reassembly 1‘ Install the fuel cock assembly on the tank w-th two screws 2. flt the front and rear rubber cushions to the frame body. The front rubber cush- lons should be Inserted by pushing the fuel tank from the rear. (Fig. 644) Install the fuel tank rear bracket on the rear cushion. Hg. 6-2: 6) Fuel strainer (up (2) o nng (a) ruel Note: When installing the tank, partic- strainer screen @ 6mm cross screws (57 Fuel - - cock fixing packing :Fuelvalve body Fuel “I" '“em'm‘ 5h°“'d be 3'" m "‘9 cock valve packing 0 Fuel cock lever o Cock condition of the wires and their routing. l ' . l , ‘ EV" 5pm; ® sem" ”me Q 0°53 “”3“ 3, Install the fuel Ilnes uslng fuel tube CleS and connect the fuel tubes to the tank valve. 4. Turn the fuel valve cock to the “ON" position and check the fuel for leaks. Ell. s—u Fuel tank IGNITION SYSTEM CONTENTS 7—1 GENERAL DESCRIPTION. DESCRIP‘IION ...................... SPECIFICA‘HONS ..................................... ,34 IGNI‘IION TIMING TEST ............................... 35 7-2 IGNITION COIL . 3‘ Description . .. b. Disassembly ......................................... 86 c Inspection . . ................ 86 d. Reassembly . ................ B7 73 SPARK PLUG ............................................ 87 a. Description ......................................... 87 b. Disassembly .................. . . 86 c. Inspection ................ . . '88 d. Reassembly ................. 89 7—4 CONTACT BREAKER AND CONDENSER .................. 89 a. Description ,. b. Disassembly. c. Inspection ............................................ 90 d. Reassembly ........................................... 90 745 SPARK ADVANCER ......... a. Description .............. b. Disassembly ........................................... 92 c. Inspection ........... dI Reassembly 54 7. IGNITION SYSTEM 7—1 GENERAL DESCRIPTION DESCRIPTION The ignition system consists of two ignition couls, two contact breakers, four spark plugs, an ignition switch and a battery. The current from the battery flows through the primary wmding of the ignition coil and circuit is completed by grounding through the contact breaker. There are two contact breakers which are located 180" apart. One of the breakers furnishes the high voltage currents to spark plugs 1 and 4; the other breaker furnishes the current to plugs 2 and 3. The contact breakers ignites the spark plugs in alternate sequence to provxde a firing sequence of 1, 2, 4 and 3. Since no distri- butor is used, the construction is simple and the system is easy to service. (Fig. 771) ® ® (D Spark plugs t3< Comm breaker {57 Battery (2) Ignition ml (9 C:nd;nlser .g. - SPECIFICATIONS Ignition coil make 7) Toyo Dense Spark plug type l Standard 1 NGK D~8 ES Optional ‘ NGK D'7ES, De1OE Size 12 mm (thread diameter), 12.7 mm (reach) Gap 0.024~0.028in (0 6~0,7 mm) Contact breaker make Hitachi 7 Spring force 1,43~1.87 lb (650~BSOgi Point gap ,7 0.012~0.016in (0,3~0.4 mm) Condenser capacity 0.24 gF:10% ‘Condenser insulator resistance Over 10Mn (1,000 meger) Spark advancer Crankshaft speed at start of advance 1,000~1,150rpm Crankshaft speed at full advance 2,3m~2,5CDrpm Advance angle 35" 7-! GENERAL DESCRIPTION as DIAGNOSIS Item Engine over heat Probable Causes l . Ignition timing out of adjustment ‘ Remedy Adjust ignition timing i 1 Spark plug does l 1. Defective ignition coil Replace not fire l 2. Defective spark plug ‘ Replace 7 7.7 77 7 777 7 7 .‘7 777 77* Spark at points ‘ 1. Defective condenser Replace excessive l Weak spark l 2 Broken or shorted ignition high Replace No spark tension cord , 3. Dirty spark plug electrodes l Clean 5 ark plug electro es IGNITION TIMING TEST An accurate timing test can be made by using a strobe timing light. Follow the procedure below for checking timing with the service tester, (Tool. No, 07308—0010000) 1, Connect the power cord to the battery and ground the black ground cable. (Fig. 7-2) 2. Set the selector knob to TIMING, 3. Plug in the timing light cable and attach the high voltage cord to the No.1 (or No. 4) spark plug head attachment. 4. Remove the pomt cover on the right Slde of the crankcase. 5. Start the engine and With the engine idling (850~950 rpm), point the strobe tim- ing mark. The ignition timing is correct, ii the F mark (1.4 cylinder) on the spark advancer is aligned to the timing mark. (Fig. 773) 6. Next, raise the engine speed above 2,500 rpm : if the timing index mark is between the two timing marks located at 23.5~26 5° ahead of the“ F” mark, the timing for both idling and full advance is satisfactory. If there is malfunction with the ignition timing even though the RPM is constant, the fault is probably with the spark advancer spring or a defect in the breaker points, therefore, the unsatisfactory parts should be repaired or replaced. if it is necessary to make adjustment, perform the adjustment in accordance with the procedure described in service adjust- ment on page 91~92. “3.7 3 Timing Iigh| JiiMiiic AlTACHMENT SPARK PLUG HEAD / 7SPARK PLUG HE Pgi \@ \ME GENERATOR ROTOR BAITERV \liMING LIGHT “3.74 Ignition timing test 86 7. lGNlTlON SYSTEM 7. The ignition timing for the No, 2 and 3 GREEN SCALE cylinders are also checked in the same TACHOMETER SWllCH (Oil) manner described above. L : I) TACHOMETER 8. The engine RPM is checked with a ta- chometer or a revolution counter located + on the tester. Set the tachometer switch (9 + to the ON position, insert the tachometer 0 cable, place the tachometer against the center of the spark advancer shaft and then read off the green scale. Hg. 75 7—2 IGNITION COIL a. Description The ignition coil of a primary coil with 380 turns of enameled and secondary coil with 15,000 turns wire wound around the primary coil, with an iron core of laminated silicon steel sheets in the center. Each secondary coil has two high tension cables that lead to two spark plugs. (Fig. 776) “5.7-6 (D Primary terminal ljijnthenciesin b. Disassembly ® High tensron (a) Primary Coil terminal (7) Bobbin 1. Open the seat and remove the fuel tank @ Case (a) Secondary Coll in accordance with section 6~3b on page 74, 2. Disconnect the electrical leads (yellow, blue and black/white leads). 3. Unscrew the two ignition coil mounting bolts and then the ignition coil can be re- moved from the frame. (Fig. 777) G) High tesion cord 6) Iron core c. Inspection 1 Bench testing ignition coil Check the ignition coil using the service tester by following the procedure below. , (Fig. 741,9) Fig.7-7 a) Ignltlon Coil @ Leads connectors Connect the power cord to the 12V (2) Mounting bolts battery and ground the black ground cord. Connect the ignition primary cord plug to the tester and connect the opposite terminal end to the primary terminal of the coil. Connect red test lead to the black terminal of the ignition coil; the white lead to the yellow cord of the left coil (right coil to the blue cord). Connect the high tension cable (red) to the secondary COIl terminalt Position the selector knob to COIL TEST. Adjust the three point spark tester to the maximum distance spark is maintained and then note this distance. The coil is satisfactory if the distance is greater than 0.23m (7mm). 7—3 SPARK PLUS 87 Note : Spark condition as shown in Fig. 7—9A is normal. Fig. 7—93 shown the spark condition when the test leads are connected in reverse at the ignition coil. figt778 lgnltlon (Oll test 2‘ Testing the coil wrthout removmg fig, 779 External battery is not required. Connect the tester ground lead (black) to the motor- cycle frame. Remove the spark plug cap and install the spark plug head attachment on the spark plug. Connect high voltage tester cable to the attachment and then reinstall the spark plug cap. Turn the ignition swrtch to the ON posi- tion use the kick starter or starting motor to turn over the engine and determine the maximum sparking distance of the cod. 3. Check the high tension cord for damage and deterioration, It It :5 found to be im- proper condition, replace It with new one. (I. Reassernbly 1. Mount the ignition corl assembly on the frame with the two bolts. 2. Connect electrical leads (yellow, blue and black/white leads) to ere harness leads. 3. Install the fuel tank carefully not to damage the electrical leads or cables. 773 SPARK PLUG a. Description The main parts of the spark plug are the electrodes, insulator and the plug body, Standard spark plug used Is NGK D-BES. However, the following types are also avail- able for different operating condition (FigJ—10) Hotter type l D—7 [5 Stan ar l D—B ES Colder type l D—10E Fig. 7—10 (D Terminal @ Gasket @ Center electrode ® Lower sealing ©Wire packlng ®Crround electrode @ Insulator .Spark gap @Shell 58 7 . IGNITION SYSTEM b. Disassembly 1. Remove any foreign matter from around the spark plugs by blowing out with com- pressed air‘ 2. Detach the high tension cord cap and remove the spark plug with the special wrench provided in the tool kit. c. Inspection 1‘ Inspect each spark plug for badly worn electrodes, broken or cracked procelain insulator. The spark plug conditions and corrective action procedure is shown below. Spark plug condition Cause Corrective action burnt Electrode coated With car— ‘ 17. Too rich a fuel bon deposit Excessive idling Poor quality gasoline 4, Clogged air cleaner Use oi cold spark plug Worn piston ring Worn piston and cylinder Excesswe clearance between valve guide and valve stem Electrode iovErheated or 1. Use of hot spark plug l 2. Engine over heating l 3. Improper ignition timing 4. Loose spark plug or dam- aged spark plug hole thread i 5 Too lean a fuel mixture ‘ s, 7 ‘ Spark plug over torqued Adjust carburetor Adiust idling Use good quality gasoline Servtce the air cleaner Use proper heat range plug (hot type) Replace piston ring Replace piston or cylinder Replace valve guide or valve Use proper heatirange plug 7 Readiust ignition timing Retighten plug or replace cy- linder head Adjust carburetor (Replace withia Séfiépark plug | l l fig.7~11 8 Spark plug 7711) Spark plug cleaner 24 Plug cleaning is best perlormed by spark plug cleaning set, however, lacking this set, a satislactory Job can be performed by using a Wire brush or stiff pin to remove the depos-ts and washing in gasoline. (Fig. 7—4 CONTACT BREAKER AND CONDENSER B9 3. After completing inspection of section 2 adjust spark plug gap to 0.024%.023in (0.6~0.7 mm). The gap can be measured ‘ by a thickness gauge. The adjustment is ' made by bending the negative (ground) electrode (Fig. 7—12) 4. inspect the spark plug hole threads and clean before installing plugs. Corrosion deposits can be removed with a 12 mmx i 1.25 mm pitch thread tap or by using a . small wire brush. L , Note: 1. Never use an improper heat range spark plug. 2. Do not attempt to dry or remove soot from the spark plug by burning. d. Reassembly 1. Install the spark plug in the reverse order of disassembly. Note : 1. The spark plugs in the No. 2 and No. 3 cylinders are difficult to reach ._ and it are is not taken during the re- "5'7 '3 6) Spam plug W'M‘h moval and installation of these spark plugs, it is possible for the plugs to be dropped and become lodged in the cylinder head cavities. (Fig. 7‘13) 2. All spark plugs must be properly torqued. loose plug will not properly dis- sipate heat and become very hot, causing possibly damage to the engine. 7—4 CONTACT BREAKER AND CONDENSER a. Description The contact breaker is mounted in the compartment which is at the right end of the crankshaft and consits of a base plate, two breaker arms, fixed and movable points, primary terminal, spring and lubricating felt. The two condensers are also located on the contact breaker base. The purpose of the condenser is to prevent unwanted sparking across the points. (Fig. 7— 14) rig. 7—14 G) Contact breaker @ Condenser 90 7. IGNITION SYSTEM [7. Disassembly 1. Remove the point cover. 2. Disconnect the lead connectors (yellow and blue leads) at the center of the frame, right lower side. (fig. 7715) 3. Unscrew the 6mm hex nut and remove the Contact breaker assembly. (Fig. 7716) 4. The condenser can be removed from the breaker base. c. Inspection 1. Checking the contact breaker point, If Oil is left for along time without removal, a hard film will be formed and eventually result in misliring. Therefore, remove onl with trichloroethy- lene from the contact breaker point. a. Dress the pitted or dirty point with either a pomt file or emery paper, how- ever, if the condition is relatively severe, remove the contact breaker arm and dress the pomts on both the arm and the sta~ . tionary point with an oil stone, making Fig-7’16 (1)6mm hex ”0' sure that the pounts will have parallel :2 Easilwbaflirw swing mews contact when assembled. The point gap should be adjusted to 0.012~0.016in (0.3~0.4 mm). (Fig. 7—17) b. Replace the breaker arm if the pivot hole worn excessively. c. Always maintain the contact breaker terminal and Insulators as well as the wiring free from water, oil, and foreign matters. d, After the points have been dressed, clean the surfaces with a clean rag soaked in small amount of trichloroethylene, further, oil or other foreign matters should not be permitted on the breaker assembly. . b 1 Fig. 7.17 6) Correct 3. Condenser capacity (2) Contact is wow Measure the condenser capacity with the % S::,::;$::3 (he mum“ service tester. If the capacity is 0.22~0.26 11F, it is satisfactory, Refer to the service tester operating instruction leaflet for the measuring procedure. d. Reassembly 1. Assemble the each component parts on the contact breaker base plate. 2. Install the contact breaker assembly with the three setting screws. 774 CONTACT BREAKER AND CONDENSER 9| 3. Install the advancer shalt special washer, 6mm washer and tighten 6mm hex nut. (Fig. 7713) 4. Connect the electrical leads. 5. When attempting the Ignition timing ad— justment, both the ignition timing and the breaker points gap should be adjusted, (1) Contact breaker point gap (Fig. 7719) Before adjusting ignition timing the breaker points must be checked Open the spring loaded contact breaker “is-743 1 Com“ 11'9”” “WWW . . i2; Conlatt breaker setting screws point by a finger and check surtace condition. 3 Advance, Sm" spew] washer if the points are erroded, pitted or burnt, a; 6mm washer rm 6mm hex nul dress with a point file and follow by polish- ing wuth unwaxed paper to remove any file dustt Next, turn the crankshaft in the clockwtse direction hold at the position where the point gap is at maximum opening and check the gap by inserting a filler gauge. The standard gap is between 0012 to 0.016in (O 3~04 mini, To adiust the paint gap, loosen the contact breaker plate locking screw and move the contact breaker to the right or left until the proper gap opening is obtained and then “time" the IOCking 506W (“8- 7’19) fig.7 19 I Coniaci breakcr points a Contact breaker plate [0(kmg screw (2) ignition timing adjustment After testing the ignition timing With the service tester, it is found to adjust the ignition timing, perform the followmg manner, a. Start adjustment from the 1.4 breaker point indicated on the base plate. b. Remove the contact breaker wire terminal unscrewing the retaining nut and connect one end of continuity light to the point terminal and hook the negative terminal to the crankcase. Rotate the crankshaft in the clockwise direction slowly to align the “F ” (1.4 cylin- “3.7m it Contact breaker base piaie (2) Base plate setting screws der) timing mark to the index mark. At @, mghi base plate this moment the breaker point should just £4) Right‘bnée PlimkseH-ng screws to open while the continuity light flickers 5’ 1'4 ‘y ‘" er ’93 9' mm" (a) 23 cylinder breaker poinls or goes off. If point opening moment is incorrect, adjustment should be made in the following manner. c. Loosen the three base plate setting screws @(Fig. 7720) and carefully rotate the base plate until the continuity light flickers. Tighten base plate setting screws. Rotating the base 92 7. IGNITION SYSTEM plate clockwise will retard ignition timing, counterclockwise rotation will advance ignition timingr d. Next connect continuity light to 2.3 cylinder breaker points. Rotate the crankshaft 180° in the clockwise direction and align the “F" (2,3 cylinder) timing mark to the timing index mark. Adjustment may be done in the same manner as mentioned in section a and b by loosening two base plate locking screws @. er Recheck the contact breaker points gaps and recheck the ignition timing with service tester on page 85~86. 7—5 SPARK ADVANCER a. Description Centrifugal advance type mechanism is used to advance the spark. As the speed of the engine increases, the centrifugal force of the advancer weight over- rides the force of the spring and starts to move outward, movmg the point cam in the direction of rotation, in other words, advances the pomt cam to produce an early ignition. The advancer assembly is mounted on the crankshaft inboard of the contact breaker point assemblyr (Fig. 7-21) Fig.7-21 If], Spark advamer b. Disassembly 1‘ Remove the contact breaker in accord- ance with section 7—4.b on page 90 2. Remove the spark advancer from the spark advancer shaft. (Fig. 742) c. Inspection Check the spark advancer spring for loss 42 (D Spark advancer of tension and also the advancer pin for ex- ® SW“ ““3““ 9“" cessive wear; replace any part found worn excessively or defective. d. Reassembly 1. Install the spark advancer to make sure that the pin is inserted into the pin hole at the‘end of the crankshaft, (Fig. 7‘23) 2. Install the contact breaker assembly in the reverse procedure of disassembly. Fig.7»23 (D Fin hole ® Spark advancer pin @ Spark advancer CONTENTS 3—1 GENERAL DESCRIPTION ,. DESCRIPTION ............ SPECIFICATIONS . .. DIAGNOSIS ..... CHARGING TEST 8—2 ALTERNATOR” a. Description I b Disassembly. cl Inspection ., d. Reassembly . 8—3 REGULATOR .. a. Description , be Disassembly. c. Inspection . , a. d. Reassembly ........ a4 SILICON RECTIFIER, .. a. Description . . . b. Disassemblyr c. Inspection . , .. dr Reassembly ............ 100 101 101 101 .. 102 .. 102 r 102 8—1 GENERAL DESCRIPTION DESCRIPTION The charging system for the CB 750 is made up of the excited field 3—phase alternator, rectifier, voltage regulator and the fuse. The alternator consists of the battery excited field coil, stator coil and the rotor; it does not, however, contain a slip-ring or brushes. In order for the stator coil to produce a constant voltage, the current from the battery to produce the exciter field is regulated to very close limits by the dual contact regulator. The output from the alternator is rectified by the silicon rectifier before being sent to re— charge the battery. The regulator has two different types of function depending upon the charge condition of the battery. 94 B. CHARGING SYSTEM The electrical current from the battery flows through the switch and into the regulator. When the battery voltage is lower than normal (less than 13.5V at the battery terminal), the current flowing through the armature away from the upper contact and the battery to the generator field coil. The strength of the magnetic field is depended upon the strength of the battery voltage. The current field cell is 1.6A at a battery terminal voltage of 12V. This produces an output voltage of corresponding strength which is used to charge the battery. (Fig. 871) RECTlFlER fm/w R/W 12V 1 BATTER [-2. iGNlTiON SWITCH . EEGQLATOR Upper . ‘ wM ‘ Relay armature Slatnr (y i To LOAD Field coil fig. 0—1 8* l GENERAL DESCRlPTlON 95 When the battery voltage exceeds approximately 14,5V the armature coil pulls the armature away from the upper contacts and closes the lower contacts to insert a resistance (10g) resistor) in the generator field coil circuit; as the result of the resistance, the current to the field coil :5 reduced to 0.7A and consequently a lower voltage I5 produced by the generator, limiting the amount of charge to the battery. This function of inserting or removmg the resistance into the generator field coil is performed by the voltage regulator In accordance With the charge condition of the battery regulate the charging of the battery, (Fig. 372) RECTlFlER , 3R W7 qyw L l; Aerie”? e- $7771 ;: ,y .. L ’ BATTERY :: ,«T—fij‘tl I ‘ , ‘ ‘7 4% lGNlTlON swncH - ALTERNATOR Zita—g} w . _y‘ , Field cowl-‘ GLTG T0 LOAD "5 m2 96 8. CHARGING SYSTEM SPECIFICATIONS 1r Alternator Type and make Battery voltage Output Polarity Weight Stator coil resistance Field coil resistance 2. Regulator Type and make Battery voltage Polarity Weight Core gap Point gap 3 Silicon rectifier Type and make Battery voltage Output Polarity Weight [0113411, Hitachi, 12V 12V 13A (—) ground 11.0 lbs (5 kg) 0.20 7.20 TlIZ-JB, Hitachi. 12v (—) ground 0.49m (022 kg) o.oz4~o.o4 in (0.6~1.0 mm) 0.012~0.016 in (o.3~o.4 mm) $3684, Hitachi. 12 V 12 V 15 A (—) ground 039 lb (0.45 kg) 9—! GENERAL DESCRIPTION 97 DIAGNOSIS Trouble Probable Causes ‘ Remedy No 1. Broken wire or short, loose connection. l Repair or replace charging lnsutfi ent charging 2. Defective coil due to short, grounding, open circuit. 3. Detective silicon diode. 4. Broken or shorted lead wire at regulator. 5. Regulator voltage at no load is too low. 1. Wiring - Broken wire, intermittent shorting or loose connection, 2. Generator ~ shorting across layer in the field coil (resistance indicated in continuity test), ~ Shorting across layer In stator coil. - Open circuit in one of the stator c0il. - Defective silicon diode. 3. Regulator - Voltage below specified value at no load . Dirty or pitted points. ~ Coil or resistor internally shorted. 4. Battery . Low electrolyte level. Replace Replace Repair or replace ' Readjust Repair, retighten Replace Replace Replace Replace ‘ Readiust Polish Replace Add distilled water 2. Generator - Layer short (intermittent shorting) 3. Generator - Intermittent open circuit in the coil. - Improperly adjusted voltage. - Defective key switch. - Dirty points. . Defective battery plates, Replace Excessive 1. Wiring ‘ charging P terminal circuit and F terminal circuit shorted Repair resulting in split wound generator. 2. Battery Replace Internal short. 3. Regulator - Excessive voltage at no load voltage. Repair - Defective grounding. Provide proper ground - Broken coil lead wire. Repair, replace Unstable 1. Wiring charging - Bare wire shorting intermittently under vibration or Repair or replace voltage broken wire making partial contact. Repair or replace Repair or replace Readjust Replace Clean 93 e, CHARGING SYSTEM CHARGING TEST DC awmerer o Dc volt meter l T Headlighl Mater lamps Ballery Taillight .4. o 1 rig. in 1. Check the battery voltage in accordance wrth procedure described m the Battery Group, page 105. Make sure that the battery voltage IS at 12 V, if not, charge the battery conducting the tollowmg test. 2. From the battery ( ,-J terminal remove the red white selenium rectifier lead and the red power lead, and connect both to the (- I terminal of the ammeter. Next, connect the battery ( > 1 terminal to the ammetcr ( ,) terminal by using a Wire lead. 3, Start the engine and conduct the test lor the [allowing two modeS' a. Set the main key smtch to the night riding position turning on only the headlight high beam. b. Set main itev swrtch to day riding position, however, do not turn on the turn signal or the stop lights. 4, Operate the engine at the dutlerent speed listed in the table below and check to see if the measured value corresponds to those shown. If the measured values are below the rated current, adjust the regulator in accordance wrth next section on page 100~101 Note: The charge current may fluctuate slightly depending upon the charge con- dlllon of the battery. 5. Also, check the battery terminal voltages for the respective engine RPM. The rated voltages are shown In the table below, \,, Engine (rpm) _ . 1,000 2,000 3,000 4,000 >000 6,000 7,000 8,000 iCharging current (A) fl 7 77‘ 7 Night riding 65 0 2.4 1.3 1,0 1.0 0,8 06 Day riding I 3 1 1 , 1 1 1 1 1 Battery terminal voltage (V) 12 ‘ 12.4 13.2 1 14.5 14,5 14.5 14.5 14.5 872 ALTERNATOR 99 . 8—2 ALTERNATOR a. Description The alternator consists of the field coll, stator coil and the rotor. Field coal and the . stator coil are mounted on the dynamo cover while the rotor is mounted on the crankshaft (Fig. {174). . “5.84 l Generator rotor r r r. C;- b. Disassembly 2 eld (ml 3 Stator (on 1. Remove the dynamo coxer and pullout the generator rotor using the rotor puller (Tool No. D7933»300m) (Fig. 8—5} 2, Remove the stator Coll from the dynamo cover by unscrewmg the tour 6mm bolts (Fig. 8 6). 3. Remmc the field corl from the dynamo Cover by unscrewrng lhe three screws (Fig. 877). m; a s r AC gmwmur rotor ,» Rmor puller c. Inspection '1. field (Oll (Onllnwly test The msulatvon and open CHCUIK condition of the field cell Winding IS (hecked With a testerr ll there is continurty between the lead Wires and the (are, the (Oil IS grounded and ti there Is no continuity between the [W0 lead wures, [he (Oil has an open Circuit, in either case, the COll I5 defective and must be replaced‘ The rated resrstance value Is 7.2m. (Fig. 8 a) i Dynamo (over ‘3‘ 6mm cross screws 2 Stator Curl A; Fleld corl nun @ Dynamo cover @ Tester (2) 6 mm cross screws 100 8. CHARGING SYSTEM 7V "' Fig. H G) Stator (CHI (2 Tester @~ (g. @ CM)?” 49 fig. :40 fig. n~ I I Q) Polnl gap (9 Lower contact (a) Armature a) Core gap (5) Yoke gap @ Spring 6) Yoke ® Adjuslll'lg Sprlrlg @ Voltage adjusting screw ® lock nut :19 Call @ Point gap adjusting screw ® Core gap adjusting screw ® Contact set ® Upper contact ® Connectors @ Regulator ® Regulator setting bolts 2. Stator coil continuity test The insulation and open circuit condition of the stator coil is checked with a tester. If there are no continuity between the three terminals, the coil has an open circuit, in either case, the coil ls defective and must be replaced. The rated resistance value is 0.2 n. (Fig. 84.?) d. Reassembly Reassernbly is performed in the reverse order of disassembly. 873 REGULATOR a. Description The regulator is a dual contact type regu— lator and if functions by opening or closing the resistance circuit to the alternator field corl, in this way, the output voltage is main- tained at a constant level. It IS mounted in the center of the frame within the battery cover. (Fig. 840) b. Disassembly 1. Detach the battery cover and remove the regulator by unscrewrng the two setting bolts (Fig. 8 11) 2. Remove the regulator cover by unscrew- ing the two setting screws, c. Inspection 1. If an adjustment |S necessary to the re- gulator alter cheking the voltage or charg- ing current by the procedure outlined in the test section, perform the adjustment by the following manner, It the charging current or battery voltage :5 too low, loosen the voltage adjusting screw lock nut and turn the adlusting screw clockwise. If the charging current or battery voltage ls excessively high, turn the screw in the opposite direction. (Fig. 8—12) ”5.842 ® Adlusting screw lock nut © Adjusting screw 6—4 SILICON RECTIFIER 101 Note : The voltmeter indicates an output of 14~15 V at 5,000 rpm at no load, the circuit is satisfactory. 2. After completing the adjustment, reinstall the regulator cover and perform a recheck of the voltage. Note: There will lye a 0.5V rise in volt- age when the low speed contacts changes to the high speed contacts in the regulator. (Fig. 8-13) lithe change in voltage is higher then 0.5V or if there is a drop in voltage, core gap should be adjusted by re— ferring to next paragraph. 3. Core gap adjustment If the surface of the points are dirty or pitted, use a fine grade emery paper and clean up the points. Check the core gap with a thickness gauge to see if it is Within the specified limits, 0.024~0.04in. (0.6~1.0 mm). Core gap can be adjusted by loosen- ing the adjusting screw, (Fig. 844) 4. Point gap adjustment If the surface of the pomts and If they are dirty or pitted, use a fine grade emery paper and clean up the points. Check the gap wnth a thickness gauge. Standard gap is 0.12~ 0.016 in. (0.3~0.4mm). If necessary to adjust, loosen the point gap lock screw, then tighten the screw after adjustment. (Fig. 8‘15) d. Reassembly Reassembly is performed in the reverse order of disassembly. 8—4 SILICON RECTIFIER a. Description As the rotor rotates three phase alternation currents are induced in the stator coil. How- ever, the currents are rectified to DC cur- rents hy the six silicon diodes which are in one unit and attached to the center of the frame. The silicon rectifier requires cooling and complete condition in negative terminal by which the rectifier is attached to the frame. Therefore it is necessary to take special care for attachment. (Fig. 3-16) Voltage (unload) (V) Generator revolunonhpm) raw—13 (9 Standard (3 Narrow core gap Q) Wlde core gap 44 at Thickoess gauge (2‘, Core gflidjuslihgjcrew I 2‘ fig.8-1S @ Thickness auge 6 Point gap ock strew 6 1| 3 __ figs—16 @ Ceneratorrotor (o Regulator Field coil 9 Battery sum coil 0 Silicon rectifier 102 b. Disassembiy Detach the battery cover and remove the silicon rectifier by unscrewmg a setting nut. (Fig. 8717) c. Inspection 1. The condition of the silicon rectifier is tested by disconnecting it from the generator and testing the rectifier function in both the normaland reverse directions Acountinuity in only one direction Indicates a good condi- tion. Continuity in both directions or no continuity in either direction indicates a defective rectifier and shouid be replaced. (Fig. 348) Note: Do not use a meggcr for testing since it will expose the silicon diodes to excessively high voltage and cause damages. 2. Observe the tollowmg precautions a, Battery polarity should be strictly observed, do not connect the battery in reverse Reversing the battery connection Will cause the battery to become shorted, resulting in a large current to flow through the electrical system and damag- ing the silicon rectifier as well as burning up the Wiring harness _\ 8. CHARGING SYSTEM "“147 (9 silicon rectifier (9 Connenor (2; Rectifier setting not Hg. 3 w b. Care should be exerosed to assure that the electrical terminals are not connected in reverse. c. Do not operate the generator at high speed With the “P” terminal of the rectifier disconnected. The high voltage produced may cause damage to the Slilcon rectifier. d, When charging the battery irom an external source such as quick charging,the lead shouid be disconnected from the ‘P' terminal of the rectifier. d. Reassembly Reassembly is performed in the reverse order of disassembly. STARTING SYSTEM CONTENTS 9-1 GENERAL DESCRIPTION ............................. 103 DESCRIPTION ........... SPECIFICATIONS. .. DIAGNOSIS ........... . 9~2 STARTING MOTOR ., .., .., ., . 105 ‘ a. Description ............... V . . . V . . . 105 b. Disassembly . . ,. V .. . . . 105 ‘ c. Inspection ............... . . . . 105 d. Reassembly.. .. . . . . . 106 1 9—3 STARTING CLUTCH . V 406 i a. Description. . .. .. . . . . 406 . b. Disassembly .. .. . .. . . . . ,. ,105 ‘ c. Inspection. .......... V . . . 105 l d. Reassembly,. .. . . ,. . V -106 ‘ 9—4 STARTER MAGNETIC SWITCH . . ..107 a. Description . . V . . . . . . .107 b. Disassembly . . . 103 c. Inspection , . .. .. . V V . . . . . 103 d. Reassembly, ............ ,..., ,.. ., ~108 9-1 GENERAL DESCRIPTION . Starter mum , DESCRIPTION A push button type starter swatch is located on the right side of the handle bar. When . pressed, it engages the starter magnetic swrtch Starter solenoid switch . , (3 in the starter circuit to close the starting cur- cuit. Approximately 120A current flows from the battery to operate the starting motor. (Fig. Battery 9—1) rig. 9-1 @. Starter button sw2 STEERING ,,,,,,, a. Description . b. Disassembly, . I. c Inspection . l d. Reassembly .......... ‘ 11-3 FRONT SUSPENSION Description ...... Disassembly,‘ Inspection . . Reassembly , . , . 909'!” llel GENERAL DESCRIPTION DESCRIPTION The steering and the front suspension have been designed particularly to provide cum- iort and prevent riding fatigue caused from long distance traveling. SPECIFICATIONS Steering handle type 1 Up-handle type Steering handle width 3189 in (810 mm) Steering angle 40" right and left from center Front suspension type I Telescopic fork Front fork oil Oil used SAE 10W—30 or its equivalent Oil capacity 7. 0~7. 3 025. (220~230 cc) “6 ll. STEERING AND FRONT SUSPENSION Item Standard value l Serviceable limit Front cusion spring l Spring outer diameter 0.992~1.008 in ‘ — 25.2~25.6 mm Free length 19075 in 18.11 in 484.5 mm . 460 mm Coil dia 0.185in — 4.7 mm Installation load 17,579 in/71.2 lbs — 446.5 mm/32.3 kg Tilt within 15" Over 25° Front fork piston r 7 Outer diameter 1.552~1.553in 1.5512in 39.425~39 45 mm 39.4 mm Taper, out of round within 0.0003in over 0,0006in 0.015 mm Front fork bottom case Inner diameter 1.555~1.556in 1.5591 in 39.50~39.534 mm 39.68 mm Taper, out of round Within 0.0012In ‘ over 0.0012in 0.03 mm (0.03 mm) DIAGNOSIS Trouble l Probable Causes Remedy Heav_y 1. Steering stem excessively tightened. Loosen the steering stem nut. steering 2. Damaged steering stem steel balls. Replace l 3. Bent steering l Replace Vvheel . Loose steering stem mounting bolts ‘ Retorque wobble j } Soft _ ‘ 1. Loss of spring tensnon Replace suspension ‘ 2. Excessive load Hard _ 1. Ineffective front cushion damper Repair suspension 2. Ineffective rear cushion damper Replace Suspension l 1. Cushion case rubbing l Inspect cushion spring and case "0'59 j 2. interference between cushion case ‘ Repair or replace ‘ and spring 3. Damaged cushion stopper rubber Replace ‘ 4. Insufficient spring damper oil Add damper oil l l—Z STEERING li7 11—2 STEERING a. Description The handle bar is mounted on the fork top bridge and is fixed with the two handle bar holders The fork top bridge is mounted on the front forks With the two front fork top bolts, the fork top bridge in turn is mounted to the steering stem with the steering stem nut. The steering stem is mounted on the frame head pipe and pivots on the upper and lower sets of the ball bearings. (Fig. 11—1) b. Disassembly 1‘ Remove the master cylinder body by unscrewing the two master cylinder body mounting bolts and disconnect the clutch cable from the clutch lever. (Fig. 1172) 2. Remove the starter lighting ignition switch and disconnect the throttle cable from the throttle grip pipe. 3. Detach the headlight assembly from the headlight case and disconnect the Wiring at the connector; 4. Remove the two upper handle holders and then remove the handle bar. (Fig. 11-3) Fig. 114 Q) Upper handle holders @ Handle bar @oooeeeeeee rigi 1171 (i) Steering handle pipe 2‘ Handle pipe holder 1 Steering stem nut i) Steering stern washer : rork lop bridge 5‘ Steering head mp thread :1. Steerlng top tone race ’3) Sieel ball 9) sreenng top ball race [lg Steering head ’ii/ Steering stem 62, Steering bottom ball rate (ng Steel ball rm Steering bottom cone race ’is Steering head dust seal ’11’2 ' I l, , _- ~1 H5. 1172 5/ Masler (yI-nder bndy (2 Cylinder body mountlng bolts @ Starter llghting ignition switch ”E H. STEERING AND FRONT SUSPENSION 5. Loosen the speedometer/tachometer hold- ing clamp and remove the speedometer] tachometer from the fork top bridge. 6. Loosen the stem nut, two front fork top bolts, three 8mm setting bolts and then remove the fork top bridge, (Fig. 114) 7 Place a support block under the engine to raise the front wheel off the ground and remove the front suspension in accor. dance wrth section 11—31). on page 120. 8. Remove the steering stem thread, Work can be facilitated by using the special wrench (Tool No. 079024000000). (Fig. 11~5) 9 Pull the steering stern out the bottom, exercrslng care not to lose the steel balls, Hg. 11 4 <1 Fork top bridge 5 Stem m: (2) Front iork lop bolts 4 Bmm sell-rig bolts c. Inspection 1 Check the steering handle bar for damage and distortion 2. Chetk the steering stem {or distortion or tracks 3. Check to make sure that there is ade- quate grease In the (one race and also check the steel balls and it found to be excessrvely worn, they should be replaced Fig.1I-5 (1) Steering stem thread wremh a) Steering stem threat] 0 d. Reassemhly 1. Apply a liberal amount of grease on the steering ball races and assemble the steel balls 18 on the upper side and 19 on the lower side. (Fig. 114:) 2. Exercise care Installing the steering stem Into the head pipe so that the steel balls are not dropped. Install the top cone race and then screw on the steering stern thread so that there is no clearance between the steering stem and the head pipe in the ver- tical direction and that the handle turns lightly through the full range of travel. (Fig. 1147) 3. Assemble the front lork in accordance with 1173d on page 121~122. “$1 76 (ti Steel balls < a .1 :7 (D StEEring stem (3 Steering stem thread I l—3 FRONT SUSPENSION I I9 4. Install the front fork bridge, the stem nut, the two front fork bolts and then fix in place with three 8mm bolts, 5. Install the speedo/tachometer unit and attach the drive cables. 6. Set the handle bar on the handle holder and mount in place with the upper handle holders. Position the handle bar by aligning the punch marks on the handle bar to the upper surface of the handle holder. (Fig. 114%) 7. Connect the electrical Wires Within the headlight case by matching the same colored wires. 8. Connect the throttle cable to the throttle grip pipe and then mount the throttle grip bracket on the handle Install the lower bracket by positioning the dowel pin into the hole in the handle bar. 9. Connect the clutch cable to the clutch lever and mount the master cylinder bracket on the handle bar. The cables,Wire harness and brake hose should be routed as shown in Fig. 11-9. rig, ii 9 .3 Clutch cable Front brake hose hrottie cable ,. wire harness (53, rm top bridge 11~3 FRONT SUSPENSION Piston type a. Description The front suspension is a telescoping oil damper type with an aluminum front fork bottom case used for lightness. (Fig. 11—10) It consists mainly of a fork pipe ® complete with piston ’4‘), a fork bottom case (5) and a cushion spring. On “compression”, that is, when any downward load is imposed on the front fork, for example, under heavy front braking, the piston moves down, compress— ing the oil in chamber “A”, and forcing it into chamber “B” through orifices “a” in the periphery of the fork pipe to lift damper valve ‘5, off Its seat On the other hand, the cushion spring, now Compressed, exerts an upward reaction to move up the piston, The piston when so moved compresses the Oil in chamber “B” and forces it back into chamber “A” through orifice “b” to provide damping action On “full bump”, or bump over- coming the capacity of the cushion spring, the pipe is moved down toward the bottom end of the bottom case, trapping the Oll In the space between the pipe and tapered lock piece @ to provide maximum damping, On “full rebound”, the orifice “b” is covered by guide 6) and the oil is trapped within chamber “B” to provide damping on the ex— tension side. ll. STEERING AND FRONT SUSPENSION Q®Izi r31 mrn®®@@§®_ . i Front cushion sprlng front fork cover Fork cover lower cushion Steering stern Front fork rib Front fork boot >5AOQOO©@@@ Fork Plpe stopper "Hg 33) Front fork pipe @ Fork valve stopper ring @ Front damper valve Prston stopper nng front fork prsron fist 1|»1o mam (3-343) (l lfimml Front fork bolt ® 47mm circllp (21; Fork piston snap ring 23x18 “0" ring @ 354611 oil seal @ Dram cock parkrng Fork top bridge ® Front fork Ipe guide @ 6mm hex bolt Fork cover upper cushion From fork duom case 3! 8mm stud bolt «3 Front axle holder 9:; 8mm rm washer @ 3mm spring washer @ 8mm hex nut “5.11-10—1 ® Front fork prpe complete ® Front fork bottom Case complete Fig 114072 '3) Front fork prpe guide <2) From fork piston (5/ Front damper valve (5) on lock prece bl Disassembly 1. Remove the front wheel in accordance with section 134 b. on page 132~133, 2. Remove the three caliper setting bolts and adjuster nut, and separate the caliper from the left front fork. (Fig. 11—11) 3. loosen the 8x56mm front fork pipe mounting bolts (located on the fork top brigel and the 10x40 mm front fork pipe mounting bolts (located on the steering stern). Pull the front fork gentle out the bottomt (Fig. 11412) Fig.1141 @ Caliper settln @ Caliper assembly bolts Adruster nut f 1-3 FRONT SUSPENSION 12] 4. Disassemble the front fork by removing the internal circllp wrth a circlip pliers and separating the front fork pipe from the bot- tom case (Fig. 11713). 5. By removing the fork piston snap ring, the front fork piston and the front fork damper valve may be disassembled from the front fork pipe. (Fig. 11714) fig.1Ll2 I from tort c. Inspection 1, Checking front fork all To maintain good riding characteristics and Increase fork serwce life, the Oil In the front fork should be changed periodically. Unscrew the front fork drain plug at the bottom of the fork cylinder, drain the Oil by pumping the forks whlle plug IS out. Replace the plug securely alter draining. (Fig. 11-15) rig." ii i lnloml lmllli .» Pllm fig 11 14 i 334611 oil soul mi from (fril’llpt'f \lahe @ frontfork pipe gulde g anr fork piston g Fork plpeslopper mg a; Fork pls|0l\ snap 1mg (9 Fork valve stopper rlrig Remove the top filler plug and fill the V. ““ front fork cylinder with 7.0~7.3 015. (220. ~230 cc) of premium quality oil of SAE V, 10W730 grade. (Fig. 11716) Securely tighten the top filler plug after filling. 2. Check the front fork assembly by locking the front brake and pumping the fork up and down vigorously. - Smooth cushion action. - Oil seepage around the cushion oil seals. Fig.11716 T Top filler plug Fig.11r15 S, Front fork drain plug 122 ll. STEERlNG AND FRONT SUSPENSlON j, front for prston rig.11-17 C? Micrometer ' 5 .,i Fig. 11 18 (1. Cylinder gauge _2, Bottom case fig.1I719 (9 Oil seal drivms Weighl (z) Oll seal dlivtng guide on seal Fig.11-20 (D Front m assembling bar @ Front fork pipe setting bolt (8mm) @ front fork pipe setting bolt [1Dmm) .1 Measure the diameter of the front fork piston. Use a micrometer to perform this check and if it is found to be less than 1.551 in. (39.4 mm), the piston should be replaced. (fig. 11717) 4. Measure the inner diameter of the front fork bottom case. Use a cylinder gauge to perform this check and if it is found to be over than 1.562in (39.68 mm), the front fork bottom case should be replaced (Fig. 11—13) I d. Reassembly 1 Wash all the parts and then assemble the pipe guide, stopper rings, damper valve, piston and snap ring in that order on the front fork pipe (Fig. 11714) 2. Assemble the front fork pipe Into the front fork bottom case and Install the oil seal using the or! seal guide (Tool No. 079473290000), (fig. 11719) Exerose care that the oil seal is not cla- maged during installations and Install the circlip into the groove in the bottom case. Note: To disassemble the front forks of motorcycles from Frame No. 1044650 to 2089878, proceed as follows: - Replace the oil seals with new ones (double lip type) (Part No. 91255—341~ 305). Replacement - The employment of new ml seals abolished higherto used back-up rings due to the change In seal width. . Apply a coat of oil to the seals and in- sert them from the piston side while rotating. 3. Install the front fork upper cover on the steering stem (above and below the cushion rubbers) and insert the front fork pipe assembly through the steering stem, and temporarily tighten With the 10mm front fork setting bolt. (fig. 11720) 4. Fill the front fork cylinder with 7.0~7.3 ozs (220~230ch of premium quality oil of SAE 10W730 grade, and securely tighten the top filler plug after filling, 5. Properly tlghten the front fork pipe setting bolts (8, 10 mm). 6. Adjust the front brake caliper by refer ring to page 147~148. CONTENTS 12—1 GENERAL DESCRIPTION. DESCRIPTION . H SPECIFICATIONS ‘ DIAGNOSIS..r....r...t.,.r..,,. ., ., V 124 12—2 REAR snocx Assonms ., v ...... .124 l a. Description ................ V. . ........ . ,.124 ‘ b. Disassembly ......................... .. .. . 125 c. Inspection ........................ ,. . ,.,125 d. Reassembly .............................. .. ,. .125 12-3 REAR FORK .. a . Description b. Disassembly . ct Inspection... . d. Reassembly ...................... 12—1 GENERAL DESCRIPTION DESCRIPTIONS The suspensions must not only absorb the vertical shock caused from the mad conditions but must also be able to sustain applied force resulting from steering function. The rear suspension mechanism-consists of the rear cushion and rear fork. SPECIFICATIONS Item Standard value Serviceable limit Rear cushion spring Spring inner diameter 1.401~1.429in. 35r7~36.3’mm — Free length 8‘74in. 222mm 8.504in. 216mm Coil diameter 0.276in. 7mm — Installation load 8.17in./66.6lbs 207.5rnm/30.2kg — Tilt within 15" Over 2.5° 124 12. REAR SUSPENSION Item Standard value Serviceable limit Rear fork Pivot bush Inner diameter 08426~0.8447in. 21403~21,455mm 0,6504in. 21.6mm Center collar outer diameter 08412~0 8425In 21.367~21,400mm 0 8386m, 21.3 mm DIAGNOSIS Trouble I Probable Causes Remedy Soft suspension 1. Loss of spring tension, . iReplaicei 7W ’7 2. Excessive load Hard suspension ‘ 1. Ineffective front cushion damper Replace 2. Ineffective rear cushion damper Replace Suspension noise i 1. Cushion case rubbing Inspect cushion spring and éQr 2. Interference between cushion Repair case and spring 3. Damaged cushion stopper rubber 4‘ Insuflrcient spring damper oil (frot and rear) Replace Replace 12—2 REAR SHOCK ABSORBERS a. Description The rear suspension is a swing arm type With a large stroke of 3.43m. (87mm). A De Carbon type rear damper IS employed on the CB 750 is of a single cylinder double acting type. (Fig. 1271) This damper is, as shown in the figure below, a double-acting type single cylinder in which nitrogen gas and oil are used to give an optimum damping performance under all bumping and rebounding conditions Over the damper is installed a dual-pitch spring which absorbs a Wide range of Vibrations or shocks and maintains the unit in accurate alignment. Another design feature IS that the cushion is adjustable for different riding, loading and road conditions. —~ . . 13.07mI332rnm> STROKErSdmIWm} . , . , j IST SET, 8169m.{207.5mm %7 2ND SET,7.972m(202.5mm- 3RD SET' 7 776irII197.5mmI fig. 124 (p lornt rubber G) Rear cushion Sprlng ® Spring seat stopper (5) Rear damper assembly @ Rear cushion upper cover © Rear cushion spring guide 1272 PEAR CUSHIONS 125 Simple type of a construction the heat radiation is good, therefore, preformance be- ing especially good at low speed, Further, vibration stabilizes very quickly. Air and oil mixture will not occur and function will not be deteriorates even when operated for extended period over adverse road condition. The difference in pressure between the front and rear of the valve IS small; since form does not form, noise IS minimized; deterioration of the damping force is pre» vented. (Fig. 5761) The rear cusion employs a dual pitch spring, the section with the larger pitch at» sorbs the large Vibration while the section with the smaller pitch absorbs the smaller vibration. This provides for exceptionally smooth riding, Further, there are three ranges of adjustment incorporated in the rear cushion, making it possible to adjust the cushion to the different riding, loading and road conditions, b. Disassembly 1. Unscrew the rear cushion cap nut and bolt, and remove the rear cushion from the frame. (Fig. 12 2) 2. Remove the rear cushion spring using the rear cushion dlsassembling tool iTool No. 079594290003). (Fig. 12—3) Note: The rear cushion (onlains nitro- gen gas under high pressure, therefore, disassembly should not be attempted because possible injury may result. c. Inspection 1. Rear cushion spring free length Measure the free length of the rear cushion spring usmg a vernier caliper, if it is under 13.11 in. (460mm), the spring should be replaced With a new part. (Fig. 12—4) , so (9 @ “5.1244 g) Piston (2,: Valve {9 Rod Compression .4 fig. 1271 2 (ti Piston [2 Valve ’3) Rod fig. 122 ll‘ Rear (“shim H swing boit i2; Cap nut _ Rear cushion spring a R-ear n-shion disassembling tool 126 I2. REAR SUSPENSION 2‘ Rear CUSthl’l spring trueness Set the spring up on its end on the sur- face gauge and measure the amount of tilt with a square and Vernier caliper. If the tilt is over 2.5“, the rear cushion should be replaced 3. Inspect the cushion damper to insure that there IS n0 fluid leakage. 4 Inspect the damper case and rod to in~ sure that they are not damper or deformed Fig. 124 it} Vernier (ahpev (3) Rear Cushion spring 5. Inspect the rear cushion stopper to Insure [E 2 4 I .1, that it is not damaged or deformed. ‘ i ‘ d. Reassembly 1. Assemble the under seat, spring and Upper case to the damper. Compress the assembly using a rear CUSth" assembly tool (Tool No. 079594251000) and lock the as- . u sembly with spring seat stopper, (Fig. 12-5) Fligku-s Q‘Sprmg seat stoppeRr h Note: Upon completing the assembly, 8 xiiléfiihlfifirrffiié‘gt‘ée Riiléiiié‘éfifiii“ actuate the cushion assembly by hand to make sure that they are not binding. 2. Mount the rear cushion on the frame with the rear cushion cap nut and bolt Note: After installing the cushion, check the alignment of the right and left cushion and also the alignment of the cushion mounting bolt for both right and left sides (Fig. 1276). rig. 1275 (a 10mm cap nuts @ 10 mm bolts @ Side grip (51 Rear cushions @ Washer l2—3. REAR FORK 127 12—3 REAR FORK a. Description The rear fork has a rectangular cross section made from pressed steel plate to provide greater rigidity at the wheel mounting which is a clamp design. One end of the rear fork is fitted to a section on the frame and the other end is fitted to the frame through the rear cushion. When the rear wheel moves in the vertical direction, the section which is fitted to the frame becomes the pivot point and the rear wheel moves in an arc. The close proximity of the pivot point to the drive sprocket posses negligible effect on the chain tension. b. Disassembly ‘l. The exhaust mufflers must first be re- moved before the rear fork can be removed. 2. Remove the cotter pin from the rear wheel axle, loosen the axle nut and remove the drive chain. 3. Unscrew the rear brake adjuster nut, the rear brake torque bolt and remove the axle to separate the rear wheel. (refer to page 137) 4. Unscrew the rear fork pivot nut and bolt, and then separate the rear fork from the frame. The rear fork side washer and the pivot collar can be removed. (Fig. 12-8) c. Inspection 1. Visually check the rear fork for bend and distortion, and if found to be excessive, it should be replaced with a new part. 2‘ Scratched and deformed part should be either repaired or replaced. 3. Measure the bores of the rear fork pivot bushing with a inner dial gauge and the outside diameter of the center collar with micrometer, and if they are not within the serviceable limit shown below, they should be replaced. (Fig. 123) (is. 1277 (7) Grease nipple (9 Dust seal cap (a) Rear fork plvot @ Pivot thrust bush bolt 9» Rear fork felt ring @ Rear fork pivot @ Rear Iork pivot bush bolt washer 4? Rear lork as, 14mmself|otknut on Rear fork (enter in Rear tushron under rubber bush collar Fig. 12—5 rig. 12,9 a, Rear fork @ Rear iork pivot bolt ® Center collar e) Micrometer (9 Rear fork @ Inner dial gauge l25 l l l l l2 REAR SUSPENSION Item Servlceable Ilmlt Rear fork pivot bush . inner dummy 0.35m. [21.8mm) Rear fork center collar . outer diameter 0.8452m. (21.4mm) 4. There are two lubrication points as shown in the Fig. 19718. It is recommended that lubrication be performed in accordance with section 19 on page 135, d. Reassembly 1‘ Apply a liberal amount of grease on the pivot collar and assemble it into the rear fork. Insert the pivot bolt from the right side while holding the dust seal caps on both sides of the rear fork, and then install and tighten the 14 mm sell lock nut. 2. Install the rear wheel. 3. Install the drive chan. 4. When the assembly is completed, adjust the rear brake pedal and drive chain ten- sion‘ (refer to page 149 and 186)