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vegasair

08 Yz450 Exhaust popping and backfiring

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Hi everyone, im new to this forum and its a really informative place. My question is about the popping and backfiring on my exhaust on my 08 yz450. I have a Yoshimura pipe, im thinking the jetting maybe?Thanks in advance for any info..

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Hi everyone, im new to this forum and its a really informative place. My question is about the popping and backfiring on my exhaust on my 08 yz450. I have a Yoshimura pipe, im thinking the jetting maybe?Thanks in advance for any info..

Set the mix screw at 2 to 2 1/2 turns out, it will have some popping no matter what. I have an 08 with the full FMF exhaust, so I've been down this road.

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If you have stock pilot jet, that could also be the reason. Install larger one (maybe 2 sizes larger, forgot the # though)

Other than that, if your header is not sealed well at the motor or at the header/mid pipe joint that could also cause popping.

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I had a 08 yz450 with a dr.d pipe and I just upped the main jet to I believe a 180 and the bike ran awsome. I had a quick adjust fuel mixture screw for minor tweaks. Also keep the air filter really clean on that thing and it will never let you down. I had 130 hours on mine when I sold it and i never did a top end of shimed the valves, but those motors seem to be bullet proof

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The stock pilot on the '08 is fine in most cases. Read:

http://www.thumpertalk.com/forum/showthread.php?p=3710599#post3710599

...and also:

http://www.thumpertalk.com/forum/showthread.php?t=327405

Then look through the '08 Jetting DB (up and down from the post below):

http://www.thumpertalk.com/forum/showthread.php?p=6980897#post6980897

There should no reason to use anything close to a 180 main jet, and it won't affect the decel backfire in any case.

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