Jetting Question # 64,250....

3 replies to this topic
  • critter

Posted January 19, 2003 - 06:10 AM


Ok, been through all the archives and any subject regarding WR426 jetting and heres my conclusion...I have a 02 WR426 Canadian model, Big Gun race series pipe, air box lid off and going to YZ timing soon. If I'm comprehending everything right I should go to stock YZ jetting as a baseline right ??? Is there a difference between US and Canadian stock jetting for YZ's and if so does anyone know what the stock numbers are ? I hate to ask my dealer for anything more than the time, they are not very accurate on things. :)

  • Steve_WR400F_#61t

Posted January 19, 2003 - 05:45 PM


First question is elevation. The higher you are the leaner you jet it. If you need all the specs on how the YZ is jetted, check out They use the Yamaha Micro-Fishe and it'll list all the parts available for the carb. Just look at was is listed as "STD" on the list. One thing to do is change your needle. The YZ uses a different, richer, needle than the WR does. This will require you to jet just a tad leaner than you think you'll need.

I just finished my jetting woes, and finally got it right. I think. I've got the same carb your bike does and I don't thing the Canadian versions use anything different there. I ride at elevations over 4500ft and at temps less than 55 degrees in the winter. I was "Guaranteed" (by one of the self proclaimed jetting experts here) that using a 168 main, 200 main air jet, 45 pilot, 75 pilot air jet, and a 55 starter jet would work perfectly with the OBEKN needle. Turns out that that was too rich, eventhough it was leaner then what I started with using the stock OBDRS needle. I installed a 42 pilot and a 165s main and it turned out perfectly. Got a good test on this too and it is running great.

If you rejet with YZ specs, make sure you use an "E" type needle and not the "D" types spec'd for the WR. Good luck and once it's right you'll know it.

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  • HaremScarem

Posted January 19, 2003 - 11:25 PM


The 42 pj and 165 main are the stock jets for 2002's. Swapping to an E taper needle was a great move. I've been all over the charts with jetting and found moving the main up 1 size to a 168 was great. The timing change to YZ had no effect on the jetting, just more punch. Check my sig.

  • critter

Posted January 20, 2003 - 10:31 AM


Thanks for the info Steve, I think I might just be able to get this right...if it ever warms up around here :)


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