During my second lap of a harescramble at unadilla, my bike quit. It shut off instantly and stopped. It has a ton of compression but i can kick it over a little. After about 50 kicks i got it running. As long as i kept it revved up it would run fine, but as soon as i got off the throttle, it just shut off. We took the cylinder apart and didnt find any problems. We also checked the valve clearences and they were fine. I put it back together and it idled for 10 minutes just fine. I rode it about 25 feet and it did the same thing again. Does anybody have any idea what the problem may be????