My blaster will start up and run fine, then all a sudden the engine will start to race and rev. until it hits the rev limiter i will turn the key off it will continue to scream, kill switch continues to scream, i even popped of the plug wire and it still races.. somehow..... then i have to hop on it and clutch it to kill it. Then i'll start it again and it will run fine for a little bit and then all a sudden do it all over again. I checked the throttle cable, carb, reed valve, and all seem to be just fine? any ideas????