Today my 425 started after several minutes of cranking. It would sputter and quit, sputter and quit. Once it stayed running if I tried to give it throttle above idle it would get rough and almost quit. When I backed it off to idle it ran ok. After idling for a couple of minutes it quit. I cranked and it backfired once and quit. I cranked again and it started right up like it was normal. I gave it throttle and it was fine. I took it from idle to full throttle and back to idle several times and it was OK. I let it run at full throttle for several minutes and it never missed a beat. Does anyone have any idea what my problem could be? I think I ruled out the cam gear because it does run. It has the newer carb with the electric fuel shutoff. Coils? Stator? TDM? Ignition switch? Thanks.