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Honda CB500 and CB750, Model Identification and Development

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Lineage of the Honda Fours

When the Honda 750 Four was introduced in mid-1969, it created shock waves throughout the motorcycle world that continue to be felt today. Four cylinders, overhead camshaft, disc brake, electric starter—the 750 had everything. The machine had not been built that could match the sophistication and total mechanical integrity of the 750 Four. It stood—and still stands—apart from all others, the standard by which other motorcycles are judged. But such overwhelming excellence does not come easily. Motorcycles like this one are not created overnight.

Unlike Honda’s other road machines, which owe much of their development history to the evolution of earlier street bikes, the Fours are largely descended from the Honda Grand Prix roadracers. A decade before the introduction of the 750, the first Honda four was built. A double overhead cam 250, it was basically two of the earlier 125cc twins that had raced at the Isle of Man in 1959, connected side by side. With four valves per cylinder, it developed 35 horsepower at 14,000 rpm. Japan had no roadracing circuits at that time, so the four-cylinder GP machine was fitted with semi-knobbies and tested on a scrambles course.

The original four was never raced in Europe however, because in 1960 Honda built two new racers, a redesigned 125cc twin and a brand new, 250cc four. Like the original, the new four was an inline design mounted transversely in the frame, utilizing double overhead camshafts and four valves per cylinder. Honda engineers apparently felt that this was a good design and used the same basic layout in all later racing engines. They were right.

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The redesigned 250 cc Four was Honda’s first completely original four cylinder design.

The new four had a completely redesigned carburetion system. The four slide-type carburetors were bolted solidly together and insulated from engine vibrations by rubber intake tubes. The throttle slides were positively opened and closed by a dual throttle-cable arrangement that actuated a common throttle linkage at the carburetors. One cable opened and the other cable closed the carburetors, eliminating the possibility of sticking throttle slides. If this sounds familiar to you, it should. Examine the throttle linkage on your CB 500, 750K1, or 750K2.

For the 1961 season, the four was modified with a dry sump lubrication system and new Keihin racing carburetors that incorporated integral float chambers and cylindrical throttle slides. Output was up to 42-43 horsepower, and in 1961, Honda won the 250cc World Championship title.

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For 1962, Honda produced a bored-out 285cc version of the 250 four to enter in the 350 class. The new “350” had 49 horsepower, making it capable of 143 mph, while the 250 had been developed to the point where it gave 46 horsepower and would reach 137 mph. During the 1962 season, the 350 was bored and stroked to 340cc, and the output was raised to slightly more than 50 horsepower at 12,500 rpm. The 250 and 350 fours took the 1962 World Championships in their classes.

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The next multi to come from Honda was a brand new, 125cc four, designated the RC146. Built along the same lines as the 250 four, the RC146 produced 25 horsepower at 16,000 rpm and featured an right-speed transmission and a transistorized ignition system. This tiny but mighty four was timed at 125 mph at the Isle of Man in 1964 and won the 125cc World  Championship that year.

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For the 1964 season, the 350 had been completely redesigned and was finally out to a full 350cc. Delivering 56 horsepower at 14,000 rpm and weighing less than 300 pounds, the new 350 four was capable of accelerating to over 150 mph. With Jim Redman aboard, the 350 again won the World Championship. But in the 250 class, the speedy RC56 Yamaha twin had become more than the Honda 250 could handle. So . . .

A new model, the RC165, was introduced at Monza late in the season as a last ditch attempt at the 1964 Championship. The RC165 had no less than six transversely mounted, inline cylinders and produced 54 horsepower at 17,000 breathtaking rpm. It was a masterpiece of engineering and technological sophistication, and remains as one of Honda's most brilliant achievements. The RC165 didn't win at Monza though and was to require one lull season of racing before it would be fully sorted out and reliable. Incidentally, there is an amusing sidelight to the introduction of the new six at the 1964 Italian GP. It seems that Phil Read, the Yamaha ace, decided to throw a scare into (he Honda mechanics, who were thoroughly enjoying the attention and excitement that their new baby was provoking. Read merely wired two extra expansion chambers onto his Yamaha twin, threw a cover over the engine, and pushed it slowly by the Honda pits. Eyes grew wide and hearts stopped beating as the rumored, but not yet expected Yamaha “four” glided silently past the more than somewhat dismayed Honda contingent.

Of course, Yamaha’s 250 twin was no match for the Honda six, even with two extra expansion chambers tacked onto it. By the end of 1965, the six had been developed to the point where it was nearly as reliable as it was fast and the handwriting was on the wall. So for 1966 Yamaha unveiled their ultimate weapon, a water-cooled, V-4, two-stroke, and Honda countered by retaining the services of one M. Hailwood to do battle on the swift six. The show then began in earnest, with neither side holding a clear advantage. The Yamaha had more power but the Honda handled better and that was it. The 1966 and 1967 250cc World Championships went to Honda, but both were contested right to the bitter end with the results hinging on the last race of the season. Hailwood and Read staged some of the closest and most hard-fought racing the world had ever seen, and by the time Honda pulled out of racing at the end of 1967 (presumably to concentrate on the development of the CB 750), the RC165 was delivering somewhere around 60 horsepower, which works out to 4 horsepower per cubic inch. The six must be regarded as one of the most fantastic motorcycles ever built.

Naturally, Honda did not concentrate solely on the 250 class during this period. Late in 1965 a brand new 125 was introduced. Each of its five cylinders displaced 25cc, and amazingly enough, the four-valve head layout was retained even though this meant that the intake and exhaust valves were limited in size to 13 and 12 mm, respectively. The 125 five was developed from the earlier 50cc twin and was therefore quite reliable right from the outset. It produced 30 horsepower at 18.000 rpm and could be twisted past 22.000 remarkable rpm with no ill effects, which was even more remarkable considering that ordinary coil springs were used to control the valves.

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At the West German GP in 1967, a new 350 appeared. A punched-out version of the 250, the new six displaced 320cc and pumped out close to 70 horsepower at 16,500 rpm. As can be imagined, it was an extremely rapid machine. But for brute strength, the honors must go to the 500 four, which was a beast in every sense of the word. The big four incorporated most of the usual Honda design features, its major difference from the norm being the wet sump lubrication system with twin oil coolers. Even though handicapped by having a mere four cylinders, the 500 possessed so much power that it was almost uncontrollable. Too much power, in fact, for its frame and brakes, which simply couldn’t handle the more than 90 horsepower churned out by the monster engine. Mike Hailwood came closer to taming the thing than anyone; even so, it was reported in 1967 that “ . . spectators shudder and blanch as Hailwood goes rushing past on the 500, obviously struggling for mastery all the way.” It was all engine.

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The speedy little 125 five

But then, the focal point of any Honda has always been its engine, and in this area Soichiro Honda has no equal. Judging from past performances, Honda is capable of producing some incredible machines and such a dynamic company is just not capable of standing still. Perhaps, tucked away somewhere within the depths of Honda Research and Development, there’s a . . . six-cylinder road bike? An eight-cylinder racing bike? A fantastically powerful Formula 1 Grand Prix car? Place your bets now, while there’s still time. As the ads say, “Sooner or later, you knew they’d do it.”

Source: Chilton's Honda Fours Repair and Tune-up Guide, 1973






New treasure has been dropped in our mailbox!

Arrrr! Thanks to Hans, you can pick some nice loot from our library treasure chest! Okay, enough of that pirate talk. The new additions are mostly in Dutch, but thanks to Deepl, I can provide you with a (mostly) reliable translation. So! Keep yer peepers peeled, mateys! Arr!

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Soichiro Honda looking to the future

Attention, this is a machine translated article by Deepl. The original can be found here.

An employee of the British motorcycle magazine MOTOR CYCLE NEWS recently met with Soichiro Honda in Tokyo to discuss the prospects for the motorcycle over the next ten years, the founder, president and technical initiator of Honda's plants, which currently produce around one and a half million motorcycles per year and whose racing machines have won no less than 15 brand world championships over the last few years.

It's hardly surprising that Mr. Honda is an optimist - otherwise he couldn't have become the biggest motorcycle producer in the world. And the fact that he knows something about motorcycles and motorcycle building should not be denied by anyone who knows that Soichiro Honda himself is the Teduvian head of the company, from which the basic concepts of all the motorcycle models originate, which - as series-produced and racing machines - have achieved such worldwide success. His vision of the future is thus also based on the optimism of a man who, as a connoisseur and expert, is deeply rooted in his life's work. "In the next ten years, he said, the great era of the "individual machine" will come. The declared motorcycle enthusiasts will undoubtedly want to buy a machine that somehow intersects with the other's." Honda believes that serial production for these customers will be limited to basic models, which will then be completed and equipped according to the customer's wishes. Of course, he is thinking of light for technical worthless cleaning, but rather of the possibility of being able to precisely fit the body dimensions of the driver: his position on the machine and the position of all of his operating levers. Not two motorcycles of the models built for this group of prospective customers will be exactly the same - he believes (the technician!).

However, he is convinced that the motorcycle markets of the coming years will have to be divided into two groups: one group - represented above all by buyers in the United States - who want nothing more than fun with their motorcycles in their spare time - and the other group - buyers in developing countries, for whom the motorcycle will be the economic transport equipment for many years to come. "At present, according to Honda, the motorcycles for these two large customer groups hardly differ at all - but in a few years' time, a single glance will suffice to determine the difference".

"Nevertheless, the Honda motorcycle will keep its shape and lines, the Honda president continued. By and large, a 1975 motorcycle of the year will still look exactly the same as it does today. Disguises (honda's personal opinion) will hardly gain more popularity than prey, apart from countries with unfavourable climatic conditions. Perhaps the team will make a comeback - but only if it succeeds in giving it a completely new line."

In Honda's opinion, the number of cubic capacity sizes will by no means be reduced, but rather will increase even more - prompted by the wishes of "individual buyers" who also want to have differentiation options with regard to cubic capacity. It is not surprising to hear from Honda's mouth the prediction that the four-stroke engine will be more important than the two-stroke engine for the motorcycles of the coming years with regard to the lighter exhaust gas detoxification. Production models with more than two cylinders will not be available due to the high production costs. But the engine capacity capacity of the engines will increase considerably in the course of new material knowledge and because the supply industry, especially the electrical engineering industry, will certainly come up with new developments - by about 50% over the next ten years.

Tyres will improve, new materials will provide better grip on the road and thus make it possible to really exploit the existing possibilities of brakes. Of course, according to Mr. Honda, the arrangement of the operating levers will be standardized. For example, the brake pedal will be located everywhere on the right - a matter of course from the point of view that most motorcyclists will also be car drivers and both vehicles will have to be braked with the same reaction.

Honda also believes that the number of motorcycle manufacturers in the world will remain more or less the same. For the small producers, he sees future opportunities especially in the hip view of the "individual motorcycle". "Of the 3 billion people currently living in the world today, only one in eight can even afford a bicycle. This is where the great future for the motorcycle industry lies - we have only taken the very first steps into this future."

This is how Soichiro Honda sees the future - for his plant and for the whole industry. Some people will be surprised that this man paints such perspectives for the motorcycle, of which one would like to believe that the motorcycle has already been written off for him and that there are only automobile plans for him and his development team of several hundred people. Admittedly, all this is true of what one hears about Honda's increased activity in motorcycle racing - and it fits right to the image offered by the Selfmademan. More than 100 patents, processed in Honda's motorcycles, protect inventions and constructions of himself. And when it is said that most of the employees in his nine-storey administration building only know him from pictures - it is because they don't see him there: his headquarters are in his development work, where he is found either on the drawing board or, with a piece of tools in his hand, in one of the workshops.

We are far from seeing Mr. Honda's views of the future as a gospel - in some of them he can be as right as he is wrong. His argumentation is indisputable, that there is still a huge sales field for motorbikes and thus great economic and technical development possibilities. Honda sees them - and will use them.

Unfortunately, this is not the case everywhere. A leading man in a German company whose brand concept was not insignificantly influenced by motorcycle construction, recently said it quite bluntly:"I hate motorcycles! Do we still have to be surprised?

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[DE] Soichiro Honda blickte in die Zukunft

English version can be found here.

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Source: Das Motorrad, 12 August 1967, issue 17, Page 3


Click on the button to toggle between showing and hiding the raw OCR souce.

Soichiro Honda blickte in die Zukunft ' Ein Mitarbeiter der britischen Motorradzeitschrift MOTOR CYCLE NEWS hat sich kürzlich in Tokio mit Soichiro Honda über die Aussichten des Motorrades in den nächsten zehn Jahren unterhalten, dem Gründer, Präsidenten und technischen Initiator der Honda-Werke also, die derzeit rund andertbal_b Millionen motorisierter Zweiräder pro Jahr produzieren und deren Rennmaschinen es im Verlauf der letzten paar Jahre auf nicht weniger als 15 Mad-enweltmeisterschaften brachten. Daß Mr. Honda Optimist ist, ist kaum erstaunlich - anders konnte er ja wohl nicht zum größten Motorrad-Produzenten der Welt werden. Und daß er etwas von Motorrädern und vom Motorradbauen versteht, dürfte ihm auch keiner bestreiten, der weiß, daß eben Soichiro Honda selbst der technische Kopf des Unternehmens ist, von dem die Grundkonzeptionen aller der Motorradmodelle stammen, die - als Serien- wie als Rennmaschinen - zu so weltweiten Erfolgen kamen. So ist also auch sein Zukunftsbild vom Optimismus eines Mannes getragen, der als Kenner und Könner tief in seiner Lebensaufgabe verwurzelt ist. Hin den vor uns liegenden zehn Jahren, so meinte er, wird die große Zeit der ,IndividualMasch. ine' kommen. Die ausgesproch.enen Motorrad-Enthusiasten werden zweifellos eine Maschine kaufen wollen, die sich. von der des anderen irgendwie unters<neidec." Honda glaubt, daß sich die Serienfertigung für diese Interessenten sozusagen auf Grundmodelle beschränken wird, die dann ganz nach Wunsch. des Käufers komplettiert und ausgestattet werden. Dabei denkt er aber natürlidl llicht an technisch wertlosen Ausputz, sondern etwa an die Möglichkeit, den Körpermaßen des Fahrers dessen Position auf der Masch.ine und die Lage aller ihrer Bedienungshebel genauestens anpassen zu können. Nicht zwei Motorräder von den für diese Gruppe von Interessenten gebauten Modellen werden sich dann völlig gleich sein - so glaubt er (der Tech.niker!). Allerdings wird man nach seiner Überzeugung die Motorradmärkte der kommenden Jahre in zwei Gruppen trennen müssen: die eine nämlich - repräsentiert vor allem durch die Käuferschaft in den Vereinigten Staaten - die mit dem Motorrad nichts weiter als Spaß in ihrer Freizeit haben wollen - und die andere - das sind die Käufer in den Entwicklungsländern, für die noch für viele Jahre das Motorrad wirtschaftliches Transportgerät sein wird. "Derzeit, so Hondas Ansicht, untersmeiden sich. die Motorräder für diese beiden großen Abnehmerkreise noch kaum - aber in wenigen Jahren schon wird ein einziger Blick genügen, um den Unterschied festzustellen." "Trotzdem, so fuhr der Präsident der Honda-Motors fort, wird das Motorrad wohl grundsätzlich. seine Form und Linienführung behalten. Im großen und ganzen wird ein Motorrad. des Jahres 1975 noch. genauso aussehen wie heute. Verkleidungen (so Hondas persönliche Ansicht) werden kaum mehr Popularität gewinnen als beute, abgesehen von Ländern mit ungünstigen klirnatisch.en Bedingungen. Vielleicht wird das Gespann ein Comeback erleben - aber wohl nur, wenn es gelingt, i'bm eine ganz neue Linienführung zu geben." Die Anzahl der Hubraumgrößen wird nach Hondas Meinung keineswegs geringer, sondern eher noch größer werden - und zwar veranlaßt durch. die Wünsche der "Individual-Käufer", die auch hinsich.tlich des Hubraums Differenzierungsmöglichkeiten haben möchten. Nich.t verwunderlich. ist es, aus Hondas Mund die Voraussage zu hören, für die Motorräder der kommenden Jahre werde der Viertaktmotor mehr Bedeutung haben als der Zweitakter, und zwar im Hinblick auf die leichtere Abgasemgiftung. Serienmodelle mit mehr als zwei Zylindern werde es wegen der hohen Fertigungskosten nicht geben. Aber die Hubraumleistung der Motoren werde im Zuge neuer Materialerkenntnisse und weil sicher auch die Zulieferindustrie, vor allem die clektrotechnisch.e, mit Neuentwicklungen aufwarten werde, erbeblich steigen - um etwa 50% im Laufe der nächsten zehn Jahre. Die Reifen werden besser werden, neue Materialien werden bessere Bodenhaftung und damit die Voraussetzung bringen, die heute schon vorbandenen Möglichkeiten der Bremsen wirklich auszunutzen. Selbstverständlich wird man, so Mr. Honda, die Anordnung der Bedienungshebel normen. So wird beispielsweise das Bremspedal überall rech.ts liegen - eine Selbstverständlichkeit unter dem Gesich.tspunkt, daß die meisten Motorradfahrer auch Wagenfahrer sein werden und beide Fahrzeuge mit der gleich.en Reaktion gebremst werden mussen. Im übrigen glaubt Honda, daß die Zahl der Motorradhersteller auf der Welt etwa gleich bleiben wird. Für die kleinen Produzenten sieht er dabei gerade im Hipblick auf das "Individual- Motorrad" durchaus Zukunftschancen. "Von den 3 Milliarden Mensch.en, die derzeit auf der Welt leben, kann sich heute höchstens jeder Ach.te auch. nur ein Fahrrad leisten. Hier liegt die ganz große Zukunft auch. für die Motorradindustrien - wir sind bisher nur die allerersten Schritte in diese Zukunft gegangen." So also sieht Soichiro Honda die Zukunft - für sein Werk und für die ganze Branche. Mancher wird erstaunt sein, daß dieser Mann soJch.e Perspektiven für das Motorrad malt, von dem man nur zu gern glauben möchte, für ihn sei das Motorrad bereits abgeschrieben und für ihn und sein vielhundertköpfiges Entwicklungsteam gäbe es nur Automobilpläne. Freilich. stimmt das alles genau zu dem, was man über eine wieder verstärkte Aktivität von Honda im Motorradrennsport hört - und es paßt gcnau zu dem Bild, das die~er Selfmademan bietet. Mehr als 100 Patente, die in Hondas Motorrädern verarbeitet sind, schützen Erfindungen und Konstruktionen von ibm selbst. Und wenn man sagt, daß die meisten der Angestellten in seinem neunstöckigen Verwaltungsbau ihn nur von Bildern kennen - dann deshalb, weil sie ihn dort nicht zu sehev bekommen: sein Hauptquartier hat er in seinem Entwicklungswerk aufgeschlagen, wo man ihn entweder am Reißbrett oder, mit einem Stück Werkzeug in der Hand, in einer der Werkstätten findet. Wir sind weit davon entfernt, die Zukunftsansichten Mr. Hondas als Evangelium zu betrachten - in manchem kann er ebenso recht behalten wie sich irren. Unbestreitbar ist seine Argumentation, daß es noch ein riesiges AbsatZfeld für Motorr'.ider gibt und damit große wirtschaftliche und tech.nische Entwicklungsmöglid1keiten. Honda sieht sie - und wird sie nutzen. Leider ist das nicht überall so. Ein führender Mann in einem deutschen Unternehmen dessen Markenbegriff nich.t unwesentlich vorn Motorradpau geprägt wurde, sagte es kürzli;n ganz unverblümt: "Ich hasse Motorräder!" Muß man sich dann noch wundern? SR

Happy new year and thank you very much!

Dear visitors and members,

The end of 2017 is nearly here and I want to take the opportunity to thank you for visiting my website and making good use of all the data that is available!


Next to 844 downloads (one got taken down by the copyright holder), the website now also holds a rough draft of all available VIN data for Honda motorbikes and mopeds. This year 1650 new registrations got added to the memberlist. At almost 2 million visits and 13,5 million page views, the Alexa rank has gone up to (currently) 2.134.804. It has even been higher, but this is a fair average. Total amount of bandwidth used for all the downloads is 451 GB.

71 Questions were sent in my email and all were answered and sorted out. From people needing a manual, questions about VIN numbers, technical questions and creating a few official VIN reports so people could resolve issues in their vehicle's paperwork.

Thanks to your donations and me selling a pile of Honda stuff, the finances are now nearly at 130 euro in the plus! That's good news for the next year and this makes paying for the hosting fees a lot easier. I'm still considering moving host to cut some more costs, but that has to be decided later.

I wish you all a happy newyears party and lots of safe miles on the road!
And again, thank you very much!