Idle screw not doing anything and jetting question 02 yz426f

5 replies to this topic
  • Sonic99

Posted May 12, 2008 - 07:47 PM


Hey guys, I just bought my first dirt bike about 2 months ago. 2002 yz426f w/ a very high flowing header and very old school pro circut race pipe. I think it still have the stock jetting because it back fires and pops quite a bit on deceleration. Right when I got the bike I put a fmf power bomb header and fmf q4 pipe on it. It still backfires and pops on decel a lot so I was hoping to get some help with the jetting. This is the first carbed anything I have ever owned so I don't know a thing about them. Can someone walk me through what exactly I need and how much it should cost? :rolleyes:

Up until recently the idle screw has worked just fine, but now my idle is pretty low and turning the screw has no effect on it... Any ideas on what is wrong?

All in all this bike is awesome though and Im having a blast with it!:thumbsup:
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  • 1998YZ400F

Posted May 12, 2008 - 08:32 PM


might be running lean. i would try to take the carb off and get a manual and familiarize yourself with it and how it works.

  • Sonic99

Posted May 12, 2008 - 08:41 PM


Yeah im pretty sure its running lean. I want to know how much rejetting it costs roughly and what all is needed to do it. That, and whats up with the idle lol.

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  • 1998YZ400F

Posted May 12, 2008 - 09:44 PM


like i said, i would learn how to do it yourself. its fairly easy and much cheaper to do it that way. you just need to buy jets appropriate for your bikes setup. i find the best way to learn is through experience. as for the idle there is an idle adjustment knob under the choke that should raise it. if it doesnt, the cable might be broken. it happened to me. i say go to town on it.

  • Sonic99

Posted May 13, 2008 - 08:33 AM


ill check the cable but does anyone know jetting pricing??

  • William1

Posted May 13, 2008 - 08:42 AM


A competent (key word) shop should not charge more than two hours labor.

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