Try pulling the air box off, and take a look inside the carb. bore. Is the slide hanging up? the idle screw in too far? The only other likely things could be the Jet(s) worked loose, or the main jet needle has come off the retainer, and is hung up too high. Turn the larger carb screw out a few turns while looking into the bore. You should see the throttle slider moving down. the smaller screw does the IDLE mixture, and if this were too far out of adjust. the scoot would not idle at all. When you twist the grip to full throttle you should NOT see the tip of the main jet needle. The last thing I could see is a bad, or frayed throttle cable. Take the top cap off the carb, pull the slider out, and twist the grip several times. the slider should feel smooth as silk w/ NO jumping, or resistance. with the throttle released try to pull on the slider to see if there is any slack inside the cable. Should be none. Try these, and please post back. You'll find it.