Running Too Rich?

when i give my '77 puch maxi sport full throttle, it takes a while to reach full speed, but if i hold the throttle back and then release it a little, it speeds up quickly and reaches max speed. basically, it runs faster when im not pulling the throttle all the way back. is this how it runs or could there possibly be too much oil in the mix?

Re: Running Too Rich?

Brian Mikami /

Do a plug chop at full throttle and see what your plug looks like, that will tell you what's happening at WOT. If it's black and wet, could be rich. Is your air filter perfectly clean? What is your oil ratio now?

Re: Running Too Rich?

it sounds like the carb is not metering fuel according to the engine's needs..

When you open the throttle wide, a lot of air suddenly streams in. This air should instantly draw lots more fuel up and into the airstream. If fuel is restricted there is a power lag while the engine only gradually speeds up because air:fuel mix is off and power is low.


So, assuming the bike is 100% stock, the problem seems to be that incoming air is not being matched with an adequate amount of incoming fuel. My guess is the main jet is clogged or the float level is low. So, it might be best to just clean and tune up the carburetor. Also look for air or fuel leaks in and around the intake manifold. And make sure fuel flow is good from the tank to the engine.

The bike was not built that way and your problem is an abnormality. Unless this bike was modified, returning the carb/fuel system to as-new condition should cure it.

Re: Running Too Rich?

I would think that the carb slide cutaway and needle taper are correct but hat the main jet is too big causing an over-rich mixture at full throttle.

It could also be a plugged up (or over restrictive) air filter.

Re: Running Too Rich?

I have the same porblem on my new moped. The owner before my told me that the bike fell on the carb so the carb became more restrictive.

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