Yz426f fuel problems

9 replies to this topic
  • 00 yz426f rider

Posted March 25, 2016 - 05:02 PM


I got a 2000 yz426f and it wont idle without the choke and will want to die when you let off the gas it also backfires when decelerating. I have read on here that if i adjust the air/fuel screw on the carb and i get it to stop backfiring i dont need to mess with the jets but i dont know where the screw is also can this fix the idle problem?

  • defilmcrew

Posted March 27, 2016 - 10:50 PM


That sounds like your pilot jet is clogged or too small (probably clogged). check for air leaks around the carb and from your exhaust also. As far as the screw its in front the carb bowl in the center at the main body. It usually is hidden in stock form but its there. If you dont have a quick adjuster you should prob get one (way easier for fine tuning as temps change or elevation). put it at 2 turns out from fully seated and start from there. If the adjustment is correct (it idles and doesnt backfire on decel or very very little) you should be good. If its more than 1 full turn from the 2 you started with you might consider a different pilot jet up or down depending. I.e. 3 total turns out go up a size 1 turn go down a size. Stock is i believe a 62 for the pilot size

Edited by defilmcrew, March 27, 2016 - 10:56 PM.

  • 00 yz426f rider

Posted March 28, 2016 - 01:09 PM


Thank you do you know were the screw is located

  • defilmcrew

Posted March 28, 2016 - 04:41 PM


Bottom of the carb in front of the float bowl on the engine side dead smack in the middle. Loosen the air boots and turn the carb sideways to see the bottom and you will see the screw. Also a great time to install an aftermarket thumbscrew for quick adjustments as the 426 is a little touchy with temp and elevation changes in regards to backfires on decel.

  • defilmcrew

Posted March 28, 2016 - 04:45 PM


Its the thumbscrew (red) in the attached file20160328_174311.jpg
Its the thumbscrew (red) in the attached file20160328_174311.jpg

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  • grayracer513

Posted March 28, 2016 - 05:03 PM


For idle speed, there should be a knurled black plastic knob on the left side of the carb.

  • 00 yz426f rider

Posted March 28, 2016 - 08:50 PM


Do you know what the black thing on the carb is.
I couldnt find out how to post a pic so here is a link to a pic that i found that looks like my carb


  • slasher729

Posted March 29, 2016 - 05:37 AM


That black knob gray is talking about. Yes that's the knob in the picture you provided.

  • grayracer513

Posted March 29, 2016 - 07:00 AM


That's the one. Clockwise for faster. 


Here's what the mixture screw looks like when it hasn't been replaced by an extended one:





Attached Thumbnails

  • click.jpg

  • 00 yz426f rider

Posted March 29, 2016 - 07:46 AM


Thanks everyone

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