when you give it throttle do the rev's seem to stay high for a few seconds then drop? if so your running too lean. thats what it sounds like choke = less air more fuel. hence for easy startingjust like a primer in a way
when i rev it up it takes off and i have to hit the kill switch to take care of it, even if I let the clutch out it stull runs i dont even have to tap the gas and it will fly around my yard