I bought a used yz426 (02) and it seemed to run fine. I did a valve check and the intakes were fine but the exhaust were way out of spec going from a 1.8 to a 2.05 shims on both. Now clearances are great and it seems to run better, but starting it sucks. I have a 45 pilot jet screwed out 1 1/2 turns which seems good. I have to crack open the throttle to start it and it will sometimes backfire on restarts. Thoughts?