i have a chinese 4 wheeler 110cc. when you put it under a load it likes to misfire and buck, like its losing power. i have taking the carb..apart and clean the jet out. i put a new fuel filter on it, and a new spark plug. its seem to be runing to rich, cause the smell of gas and the plug sometime comes out wet. and i tried ajusting the fuel mixture.  

the fuel mixture can set anywhere from 1 turn out to 2 turns out.

it could be a timing issue though as these are bad about breaking the valve keepers and also at jumping time.  

thanks i will try to see it thats is whats going on with it...