Yz426 issues

3 replies to this topic
  • supercornfish

Posted February 13, 2013 - 08:35 AM


Hi guys. I'm new here. I just recently got a 2002 yz426. I rode it for one day, not hard, and the lower end scrapped out. Needless to say I got another motor and got it all put back together. The issue I am having is that the bike seems to be loading up. I got it to run for about 2 minutes the first day. Since then it has only kinda sputtered. I took the carb out and cleaned the three jets I could get to easily. And still no bang. I reset the float adjustment to clymer manual specs. I believe it was .35 inch. If u have any advice that would be awesome. The carb is off the 02 motor and it is a keihin flat cr if it makes a difference. Thanks

  • grayracer513

Posted February 13, 2013 - 09:03 AM


Sputtering and misfiring could be the result of using the wrong spark plug. The bike should have an NGK CR8E, or one of the iridium variants, or an equivalent heat range in another brand. Any colder and they'll foul it.

The question otherwise is whether it's rich or lean. Lean is characterized by stumbling and gasping for air when the throttle opens or the engine is loaded, while rich is characterized by "blubbering", a regular, sputtering misfire effect.

Check the carb slide. The vacuum release plate may be installed upside down, or it may be cracked or broken. Also check the seal between the plate and the slide.

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  • supercornfish

Posted February 13, 2013 - 07:55 PM


Awesome thank you. I'm a little confused on what the slide plate is. Is it behind where the throttle cables hook up? Sorry this carb is funky to me. I did find out that my ignition coil was bad. It's weird because it fired up the other day but loaded up pretty easily, but maybe because it had weak spark. I ordered one should be here in a couple days. I'm hoping that solves it

  • supercornfish

Posted February 13, 2013 - 08:00 PM


Ah sorry I realize what the slide plate is now. Lol. It seems to be good to me. But I'm not quite sure how to properly check it

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