Help!I have a 89' Yamaha 350 Warrior and it barely has enough power to move itself. It starts and runs fine, but if you snap the throttle open, it will die, and if you slowly open it up, the engine revs up fine. The engine doesnt make and noise, it sounds tight, but it backfires through the carb when the engine is reving down and the problem is getting worse. Now if you start it up and rev it up the exhaust header gets red hot within a minute, I've never seen anything like it. Carb and valve timing is good. Thanks.

Trevor, September 2009

We don't get this one in the UK but I think your bike has a seriously weak mixture - i.e fuel starvation. Make sure the air cleaner element is in place, and check the carburettor mounting stub for leaks or perforations. Take a look at the spark plug - if the deposits on it are nearly white then I'm not far off.

John, September 2009