need yz426 jetting help

4 replies to this topic
  • yamarider426

Posted October 02, 2010 - 11:55 AM


I have a 02 YZ426 and I am having probs with the idol running. It starts fine runs great but I have to have the fuel screw out around 3-4 turns to make it not pop after decel. It also won't drop to idol after blips.

Stock jetting, clean carb, blue wire, fmf head pipe with stock cannister, no lid airbox. I'm thinking of going from a 42 pilot to a ada0 or 55 (I think this circut is too lean).
I've owner it for about 6 mths and its always had this prob. Any guesses?

Thanks in advance!

  • DeeCee

Posted October 03, 2010 - 12:56 AM


Have you checked for solutions in the "sticky's" at the top of this forum ? There is a lot of good information for 426's there.

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  • grayracer513

Posted October 03, 2010 - 12:25 PM


If it used to run, you probably have a pilot jet with a film of varnish in the jet orifice. Refer to the link in Common Threads on cleaning jets.

  • yamarider426

Posted October 03, 2010 - 04:25 PM


Put a 52 in it today and is a little better but still acts like it needs more... Gonna try a 60 tomorrow but that just dosent seem right???

  • grayracer513

Posted October 03, 2010 - 07:34 PM


Check the float level, and the pilot air jet. The 52 is way bigger than normally needed. Look for an air leak, check the hot start, and the valve clearances.

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