This has happened twice to me. Feels like a fouled plug bike wont clean out on higher rpms. Did this to me in a race for about a half an hour then cleaned out and ran good. Did the same today and let it sit and tried it and ran fine. WAS GONA CLEAN CARB AND REPLACE PLUG tomorrow but was wandering what you guys think. What plug are you guys running. I am still running stock plug. Thanks