I have a 2005 Pro 280 and it is not running too well. After a few hours riding the bike will begin to misfire and basically run terrible. The spark plug will be very black and replacing the plug will allow about one hours use before the problem occurs again. If the bike is left to cool down the bike will run fine again on the original spark plug until it is warmed up over around 2 hours use.

BVM have no idea what is wrong, and I was wondeirng if anyone on this forum had an idea. I run a moxture of 75:1 on a standard carb on the standard factory carb settings.

Any comments welcome

That sounds like some electrical component breaking down with heat, not anything to do with carb or mixture.

Ive got exactly the same problem with my 05 250,i've got a keihin carb on mine and i thought it might be fuel mixture ,but by the sounds of it it probably is'nt

Well mine's in BVM on the guarantee and even after Steve Saunders took it out for two hours he cant find the fault. Sods law it runs perfect as soon as I take it to the dealer. I bet when I get it home in a few days it will start playing up again. Steve has no idea but cant diagnose it until it starts playing up