Hey. I have an 02' blaster with a Toomey B1 pipe, a 310 main jet, and a K&N air filter without the airbox lid. It ran fine for about 2 months with the new pipe and jetting and then all of the sudden it started to bogg out and sometimes backfired. So I took apart the carb because I thought the jets would be clogged up but they were fine. So today I put a 300 size main jet in the carb and it ran great for about 10 minutes but then it started doing it again. It just dies at like 1/2-full throttle but it doesnt backfire any more. The pilot air screw is in the right position and the needle clip position is the third one from the top. I have an extra 290 jet should I try running that or will it lean it out too much beacuse even when I ran the 300 size main jet it ran good but I think it might have been a little lean because there wasnt much exhaust smoke. The only thing I can think of is there might be an air leak somewhere. There is also an exhaust leak where the exhast connects to the cylinder because there is alot of oil around that area could that have anything to do with it? I think it needs a new gasket where the ehaust connects to the cylinder.
P.S. there wasnt any change in altitude or temperature when it first started running poorly