The problem I'm having is that when I twist the throttle quickly the motor tends to stumble. It doesn't matter what gear I'm in (will do it in neutral.) If I twist the throttle at a somewhat slower pace then the motor is fine. It acts like it can't handle such quick twist of the throttle. I'm not sure if this could be a jetting problem or just typical of a four-stroke motor. Having just switched from a KX500 I'm not sure what to expect. Seems that it should be better than it is though.