Originally Posted by lucasislight

i think that "air acrews" are a 2 stroke thing, there is a "mix screw" on the carb, underneath after the carb bowl and before the intake manifold, you need a flat head bit to get to it. this screw only regulates the amount of gas going to the pilot jet. when you checked your plug, did you just let the quad idle then turn off, or did you ride for a little while then turn off? if you just let it idle and then checked, your pilot is too rich, make sure the screw is 2.5 turns out. if you rode it and then checked the plug, your main jet is probably too rich.