I'm a small engine guy but I've been given this 2 yr old Chinese ATV 150cc. It won't idle without constant goosing of the throttle, and spits and sputters at high revs. It runs smooth midrange without load but bogs heavily if I try to drive it. The KF carb PZ2 cast into the side has one adjustment screw on the side behind the plastic attachment for the throttle cable and a screw at the bottom of the float bowl. It smells rich. I can't find any information on what adjustments and how to set them up. Anything I can find talks about multiple adjustments that this carb doesn't have. Anyone able to shed some light?