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Ch35450

Jetting problem?

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Recently bought a '07 yz450f, in great shape, but I believe it is running a little lean...backfires and pops on deceleration and it idles up and down constantly when in neutral or when clutch is engaged. Has a fmf exhaust with the powerbomb I believe it's called? Correct me if I'm wrong.... and a hindle pipe, I'm wondering what I should run jetting wise? At about 300ft above sea level aswell as 0 to 30 degrees celsius, any help is appreciated thanks!

Edited by Ch35450

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Have you gone through the process of setting your idle properly, I found that will tell you if your pilot jet is right. You probably need to go one size up or maybe it just needs to be cleaned.

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Have you gone through the process of setting your idle properly, I found that will tell you if your pilot jet is right. You probably need to go one size up or maybe it just needs to be cleaned.

Yeah I messed around with it for a little and it still responds fine but even set at a lower idle it will still wander up and down by itself

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Wandering idle is a lean condition, likely caused by a dirty carb.  Also these bikes tended to be jetted lean which can also cause a hanging or erratic idle.

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The wandering or "hanging" idle can also be caused by tight intake valves.  When they're too tight, they set up a lean condition by leaking combustion chamber pressure back into the intake tract and disrupting the airflow.

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