make sure there's enough free play in the throttle cable so that the carb shuts off with an audible click when you let go the twist grip, if you have the screw-on type carb top cap make sure it's screwed all the way on, if that doesn't work turn the air screw inwards 1/8th of turn at a time, it's the small slotted head mixture screw on the side of carb, to richen the idle mixture.
Perry, May 2013