I have a 2001 400ex and last year I had the bolt that holds your stock air filter on get sucked through the carb and ate a valve. Since I got it back the idle is all over the place. Ill set it and the next time I stop it will be revving high but the next time it will be OK. Is it possible to have a vacuum leak making it do that? Any ideas? [img]i/expressions/face-icon-small-confused.gif[/img]

 

Try richening up the pilot screw 1/2 turn at a time. A lot of times, an erratic idle like that is caused by a lean pilot setting.

 

I put a friends carb that I know ran like a top on it and the same thing is happening. ???