jetting help

[gratzracing24]

Ok well i have a k&n air filter and a pro circut pipe...its was on there when i bought the bike and the guy said he never jetted it so its ran fine for like a year but now i dont kno y its like sputtering it will stay running but just kinda miss? i dont know how to explain it...but my friend is saying its the jetting...what size jet do u think would be the best to run? thanks for any help!

[400ex men]

sell that 300 now b/c you have ****ed it up:eek2: :huh

[mojoe2878]

try a new plug and cleaning up the carb. and while you have the carb. apart go up a jet size or 2 to compensate for the filter and exhaust, this should have been done from the begining. hopefully you havent messed anything up running it lean.

[gratzracing24]

I put a new plug in it like 3 weeks ago and and cleaned the carb a few weeks ago and it ran fine then it started doin this like 2 weeks ago and i havent riden it since...what would it have done and how would i fix it?