I was wondering if you might have a sugestion on where to go from here. My buddy has a 2002 YZ 426. We have checked the carb. all jets and needle are stock. The air screw is out 2.5 turns. If we put a new sparkplug in, the bike starts with one kick and will start all day very easily. Once the bike cools down ( the next day) you can kick it all day long and it won't start. Looks like the plug is fouling....black and all carboned up. Could it still be a carb. prob. We are at a loss. Any suggestion would be appreciated. Thank you in advance, Darren Mahler New orleans, La.