[PBJ250]

I have an 04 trx400ex that is backfiring, changed plug, checked valves, cleaned filter. need help!

 

[TRX2fiveO]

Welcome to the forums....Back firing how? when you hit the throttle? or when you let off of it? improper jetting will cause back firing... ie too small of a slowjet after modifications have been done, also a leaking exhaust system will cause a back fire.

 

[69quadracer]

Agreed ^^^!! Welcome to the forums.

 

[Helmut]

Welcome to the forums. I also agree with Moose.

 

[PBJ250]

Thanks i will give that a try