I have a 1987 CHAMP 100 that was loaned to me. When I got it the gas was empty, oil level was good and needed a charge. Charged it and added fuel, got it going and the idle speed was crazy high, after a minute or so it finally went down to a crappy idle, boggy throttle.

Ordered some new gaskets and then took the carb off for cleaning. Went through the jets with carb cleaner, compressed air and all other openings that I could. Put it back on and same thing...initial start was crazy fast idle then it would barely idle after a few minutes.

The I noticed the idle screw is all the way in? So on a “empty” start up it runs like it should, but after a bit even at a high idle setting it barely runs. In taking it apart the air cleaner tube has some fuel in it and I noticed the plugs foul easily and are wet if I shut off the bike and pull the plugs.

Float height seems to be with in check .8 inches or so. Can this really be a needle issues? It has the rubber tip and SEEMS alright. And fuel doesn’t leak out when the bike is off so to me it’s closing, right? Could be a great running bike it seems but something simple in the carburetor is messing me up. I know, I said simple and carburetor in the same sentence.

 

A Lot of time False air will provide symptoms like that. I am not familiar with that model but if it has a rubber mounted Carb check that closely for cracks or loose bolts where uncarbureted air could get in.

Very unsafe but often times a unlit propane torch on low will detect vacuum leaks very effectively.