i have a 2008 450r that was stock until i added a vent to the air box, threw in a uni filter, and upped the main jet from 122 to 130. my brother just got the wise idea to cut the back half of my baffle off in the stock pipe and reinserted it. it sounds great but i was wondering if that is going to affect my backflow and hurt my wheeler? it seems to run great and i pulled the plug and it was a little black so at least it is not running lean. any suggestions or comments?

 

That should make it lean, but if the plug is fine sounds like you are still in the ballpark. Be careful however, because a lean engine will give great performance, up until the point where it melts down.....