Honda Amigo - Replacement Carb?

[Jeff Brand]

Greetings from the USA!

I have a Honda Amigo, PF50R. It's the Belgian model so it's restricted to 40kph. I'm trying to find a bigger carb but I'm having a very hard time. The higher-end stock carb is a Keihin F5A. I've learned of someone else using a Keihin PA005 [A] QCR.

Does anyone know where I could find these sorts of carbs online? Thanks!

[Peter van Geelen.]

Greeting from The Hollands, Jeff!

My question is how fast you want to drive on this push-rod engine? You will have pretty bent sticks as soon as you continue to go over 60 kph, so don't overdo it.

I assume you have a carburetor similar to this one:

http://www.4-stroke.net/en/pc50-and-pf50-carburettor

Before spending money on a bigger carburetor, do check if the intake/exhaust is not limited and the flywheel limiter mechanism (if applicable) is locked with a screw or spot-weld. If all the restrictions are removed, you can then start to experiment with an old carburetor. I've driven with drilled out venturis, but I'm not sure if that is always a fool-proof method.

I've tried to find some other carburetors, but as I have to go to work now, I can have a further look tonight. Basically, those Honda engines even work on two-stroke lawnmower carburetors, as long as there is a good fit. It's a matter of experimenting.

[Jeff Brand]

60 kph would be great. I'm not sure I'd trust it past that anyway.

That's what my carb looks like. I have the old-type F4A. I'm not looking for a "high performance" mod as much as a higher-flow one that's close to the faster stock models.

What am I looking for as far as the flywheel limiting point? Would the exhaust just be clogged or would there be an extra baffle?

[Peter van Geelen.]

What am I looking for as far as the flywheel limiting point? Would the exhaust just be clogged or would there be an extra baffle?

If I'm not mistaken, there is a mechanism built in the flywheel what changes your ignition timing as soon as the speed gets too high for the engine (read: the law) You can fix this by locking it in place so the engine has room for higher RPMs. You can also change the gear ratio a little to gain speed, but that will cost you your acceleration speed.

A clogged exhaust could be possible, but since it's not a two-stroke engine, the only reason for it to clog would be due to oil leakage. I'm trying to find an example picture of a 6mm hole i drilled into the exhaust to relief the pressure even more. Normally, the exhaust pipe is not "squeezed" to limit the speed, but drilling that extra hole can help a bit.

To describe it verbally, if you look at the exhaust pipe, you notice that it has two folds. One on the top, the other on the bottom, all along the baffle. At the backside, the baffle tapers in till the actual (tiny) hole. If you drill a 6mm hole on the inner "half" of the pipe near the back, so the backside of the fold, the excess pressure will be easily released and thus your engine has more chance of running faster. This description may be confusing, but that might also be caused by my lack of sleep  :hurr:

I'll try to find a picture for you tomorrow.

[Peter van Geelen.]

Some pictures of a Mikuni carburetor I took off a running PC50. So these also seem to work... >.>

1:
Throttle slide: 17mm
Venturi size: 16mm (approx)
Type (?): E221

2:
Throttle slide: 17mm
Venturi size: 16mm (approx)
Type (?): P971

Only thing now is to look for that drill hole I was talking about :)

[Jeff Brand]

I've seen a timing advance on a Honda 50 (C102). I imagine I'm looking for the same thing, but in reverse and with the opposite effect.

The law here would allow it to go up to 50 kph (30 mph). I can't actually find enough information about the Amigo here and hope to get it registered as a Novio (the US version of the Honda PF50.) If I can't do that, it may never be street legal.

I'll try the exhaust next, and the carb hunt continues. I should also find a new air filter. The filter paper is quite old. I'm not sure if I should find new paper or an aftermarket one that fits under the foot rest.

Thanks for your help so far.

[Peter van Geelen.]

I've seen a timing advance on a Honda 50 (C102). I imagine I'm looking for the same thing, but in reverse and with the opposite effect.

Indeed!

The law here would allow it to go up to 50 kph (30 mph). I can't actually find enough information about the Amigo here and hope to get it registered as a Novio (the US version of the Honda PF50.) If I can't do that, it may never be street legal.

The Novio is the PF50, so it should not be a big problem, I think. Maybe dare (*) a call to the DMV?

(*) From what I have seen in series, the DMV is a nightmare ;)

[Jeff Brand]

I did exactly as you suggested. I replaced the spring with a wire to keep the arm from moving and immediately gained 5-10 kph. I was also told to advance the timing to just before the F line to gain some more, so we'll see how that goes.

The DMV can be tough but I'm in a smaller city so it's a little less frustrating.  :grin:

[Peter van Geelen.]

Great to hear that it gave immediately results! And advancing the timing is indeed also a good idea, forgot about that ^^

Also, since you will now put some more "load" on your engine, it is a good idea to keep an eye on your oil level and quality. And while you are at it, the recommended valve tappet clearance is 0.05 mm for both valves, but I always make the exhaust clearance a tiny bit looser to 0.08-ish. This way your valve has a fraction of a second more time to release its heat to the valve seat.

[Jeff Brand]

I have no idea how to adjust those tolerances. What tools will I need to properly measure those clearances?

I have some generic 4-stroke oil. What do you recommend?

[Peter van Geelen.]

Alright, first of all, you need a so-called feeler gauge, which you can see here: http://en.wikipedia.org/wiki/Feeler_gauge
They can be found sometimes cheap in the dollar bin at the gas station.

Settings to remember:

Intake valve tappet clearance : 0.05mm (0.002in)
Outlet valve tappet clearance : 0.08mm (0.003in) (note that this is not the factory setting, but a setting "from experience"

The picture of the cylinder head you see is from a PC50, but that is the book I have at hand now. PF and PC do not differ in the way of adjusting the tappet clearance.

Here we go:
The tappet clearance will have a great deal of effect on the valve timing. Further, if the clearance is too small, it may prevent the valve from fully closing and result in pressure leak at the valve or even a burnt valve seat. On the other hand, an excessive tappet clearance will produce tappet noise, causing noisy engine operation. The tappet clearance will also have a varying degree of effect on the engine power output and engine operation.

1. Remove the dynamo cover and align the timing mark "T" on the flywheel with the timing index mark on the crank case. To be absolutely sure that your piston is at the top-dead-center, remove the spark plug and carefully feel the position of the piston with a small screwdriver.
If you do not want to do this, then you can check it by feeling both rocker arms. They should be loose at the "T" mark. The screwdriver way is better, because it also gives you the opportunity to clean and check the spark plug.

Figure 1.8

2. Remove the tappet adjusting cap on the cylinder head and check the clearance between the adjusting screw and the valve. If the valve is actuated by the screw, rotate the flywheel one complete revolution and realign the timing marks to set the piston at top-dead-center (TDC) of the compression stroke. Check the tappet clearance with the gauge to see if it is of standard clearance as described in the list above. If adjustment is necessary, loosen the adjusting screw. Lock the adjusting screw after adjustment has been completed.

Figure 1.8

How to FEEL the thickness: It's always a debate what is the best way to determine the correct clearance, but my way of feeling is if you have to wedge the gauge in and the gauge is really difficult to move back and forth, then the clearance is too tight. If the gauge easily slips through, the clearance is too loose. When you move the gauge back and forth and it's moving "sticky", then you are on the right way and the setting is probably right.

Of course, there is no such thing as a 0.08mm valve gauge, that would make things too easy. So, of you have set the exhaust tappet clearance to 0.05, loosen up the screw a very tiny little bit. That should cover it.

NOTE:
1. The adjustment must be made with a cold engine.
2. Hold on to the screw while tightening the cock nut. Sometimes the screw is dragged along a bit while locking causing a tighter clearance.

[Peter van Geelen.]

And in regards to the oil, best would be 10w30, mineral oil.
Do not, and I repeat, do not use oil with extra lubricants like Molycoat and Teflon, this will absolutely ruin your wet clutch.

[Peter van Geelen.]

Any news? :)

[DAX6]

Dear sir,
I've read the hole conversation between you and mr. Peter.
Did you buy the machine in Belgium or Holland. The Belgium type are far more faster.
Specification for Belgian carb.F4A(F5A)
There are also differences in the crankshaft.

These parts are possible still available in Belgium.
Those engines will reach 65-70 km/hour.
cheers
Herman 

[Jeff Brand]

It's been a while. Sorry for not following up sooner. I forget to check back without some sort of email notification. :)

I hadn't taken my Amigo out for a while until the other day. It's back to its old behavior, struggling to go past 40kph. I think I have the following issues still:
1. The air filter was a major cause of problems. I'm running without the filter paper but will create one with coarse foam.
2. The timing was advanced. I haven't changed tappet clearances but I will look into it before I take it for extended rides.
3. I think that the jet is too small. I've learned that the backfiring I hear while coasting is a sign that I'm lean on fuel. I learned through the Facebook group that carbs for the Honda Monkey Bikes (Z50) are bolt-on replacements. $55 USD on eBay is a small price to pay, and I can hopefully find jets for it easily.

DAX6: The machine was made in Belgium. According to the parts list, the Belgian model was limited while others weren't. I'm interested to learn more about the crankshaft differences, though.