fmf factory 4 silencer

I have a 03 yz 450 and I can't seem to get the factory 4 to work with my bike. I get alot of backfireing on deceleration. I tried playing with the pilot screw but no diffrence at all. The bike works awesome with the stock pipe and I am running out of patience. Any help would be appreciated.

Sounds like you need to bump up your jetting. Try going up one your main and possibly your pilot. Might need to go 2 up.

yeah, any time you put on an aftermarket free breathing pipe you most likely need to "up" the main jets a couple.

I replaced my stock pipe with an FMF Ti-4 pipe and only had to mess with the fuel screw. If where you are puts you right on the edge of being lean with the stock pipe, then the FMF pipe could have put you over the edge. HOWEVER, as many people have told me, one of the most common causes of popping on deceleration (let's call it excessive popping on decel) is a leak in the exhaust system. Check the mid pipe joint for air leaks. When in doubt, pull it off and seal it with a high temp exhaust sealant. I would do that first before diving into jetting issues.

Check the mid pipe joint for air leaks. When in doubt, pull it off and seal it with a high temp exhaust sealant. I would do that first before diving into jetting issues.
And you'd be right.

Besides, decel popping is meaningless unless it's just really excessive.

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