i have been trying to get the right jetting on my 2004 YFZ450 for a long time now and i cannot get the right jet. I got a pipe, air filter on it and i put a 165 in it and it ran good, then i did the cam mod and i put a 168 in it and it sputters when i go real fast and let off and it backfires and everything. before i had that 165 in, the business put in a 170+ something and it did the same thing. so i need to know with what mods i have, what main and pilot jet should i put in? the i am at like sea level or pretty darn close to it, down by corpus christi texas

 

If its backfiring when you let off the gas to decellerate your pilot jet is rich. Try changing that one. If it rides fine with a certain main jet in keep that jet in and work on your idle jet.