go search

I recently purchased a 02 WR426, and have found this site. I tried to search through the files, for all the posative mods I can make. I see I can retard my exhaust cam one tooth and get more mid and upper. Problem is the technical link in this site, that would explain this procedure doesn't exist. Same problem for this BK mod, or grey wire.

Next issue that chaps me is the carb jetting. All I find is lots of specs for the 400 and little for the 426. The best I can guess from searching is MJ158, MAJ-160, Needle DMM or EMM, APJ-.024, PJ-35, SJ-60, Throttle stop cut, Air box lid off, grey wire cut.

Looking into my manual I see no listing for these two needles, and they don't list such a low PJ. This makes me gun shy, on making these changes.

I have attempted searching through the files, yet I find little on the 02 WR426.


I’m surprised you can’t find specs on the 426. There is little, if any, difference between ’01 and ’02, so anything that works for a WR 426 will work for your bike.

Not everybody agrees, but all three WRs I’ve jetted run great with YZ jetting. I figure if you change the cam timing, uncork the exhaust and lose the air box lid you have a YZ motor anyway. The principal difference being the E (YZ) vs. D (WR) taper needles.

For more jetting help we would need to know your climate/elevation.

I don’t know what you mean about the tech section of the site, but you can refer to the manual section that covers valve adjustment and follow that to change your timing. While you’re at it you might as well check the valve clearances and write down the shim size so you know what size to order when they do begin to go out of spec.

The jetting you list in your post seems very lean to me. If you were at sea level I think stock YZ jetting would be an excellent starting point (162, 42, 100 PAJ, EJP #4).

Finally, what does “APJ-.024” refer to? You cannot change the accelerator pump jet on the 426.

Hope this helps.

I live in Portland, OR at about 600 elevation. I have ordered the EJP and DMM needle, with much frustration at the parts counter moron. The EJP was easy to find, but I had to convince him to find a catalog on just the carb to find the DMM needle. I wanted to get a 160 MAJ along with these needles but had no luck. Could anyone give me a parts # or a way to get one.

Also could use a way to get the 100 PAJ. I don't have much confidence in my local bike shop.

02 wr426, uncorked, throtle stop cut, working on getting info for more mods, like the grey wire and BK mod, not sure if I want the YZ timing

Better to be looking at it than for it. :)


try Sudco at 1-800-998-3529 for the paj.

oddball, hunt around a little more and look for Motoman's home page. I have it bookmarked on another computer, but not this one, sorry. He has a write up on the cam timing change that I found quite usefull when I did mine. Lots of other good info there as well.

I agree Old_Novice , a wealth of information there. :D:):D

Where he shows how to do the YZ timing was very helpful.

A welcome addition to the favorites folder.


Hey guys,

I can't give you a big enough thanks for Motoman's site. I am totally stoked about the easy reading and pics on this site. I'm going to do the BK mod today. The bog from cracking the throtle open, has been driving me crazy. I'm still going to redo the carb jets, but feel that this BK mod is going to make all the difference.

Thanks for the info

Jason :)

Race Tech wont be linking to Motoman's site anytime soon will they? :) LOL

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