2002 WR 426 to YZ: jetting question.


With the clip on the #4 position, the bike was a little boggy(rich) on the low end. #3 position leaned it out and now runs without hesitation.

James Dean recommended these jets to Wayneo426 as a good place to start. I just made a few minor tweeks. The OBELN needle comes off the wr250f parts fiche. The taper of the needle is less abrupt than the YZ needle so you don't get the hit in the lower mid rpm. I'm verry happy with the way my bike runs now and have no plans to tinker with the jetting any further.

Hope this helps with your decision,



I'm no jetting expert, I spent hours on this forum and did alot of reading. JD is from the same area as I, so I knew his advice would be good. I also talked to some kids whose friend bought JD's WR400 and said it ran perfect!

Originally posted by Taffy:


my M was right to rich and your Q was rich you say? this all depends on how you set the PAJ as well. If you're still running 75PAJ then it's very lean. what are you running and what differences did you make to the APJ?


I dunno Taffy. I still don’t think you appreciate my altitude. A mile of elevation is no big deal in the Western US. Dry, hot deserts are the norm out here. In my 34 years on this earth I’ve only ridden a dirt bike below 3k feet one time. Once. When I went to Glamis a few years ago. Because of this maybe I should opt out of jetting discussions altogether. I don’t know. I’ve never jetted a bike at any “normal” elevation. I’ve owned a few bikes that I leaned the jetting on before I even rode them (my ’99 KX500 and ’01 YZF being the most recent examples of this, although I just changed my ’01 to the jetting I had arrive at in my ‘00).


Needle straight: Q is good, P is too rich, R just a bit too lean (and IMO this is an annoying place to be overly lean), all tried in the 38 to 42 pilot jet range (all at base elevation of about 4k, avg. 15%-30% humidity, 70-90 deg. F).

My PAJ is around 80 or 85. Smaller than that and I lose response at tickover, larger than that and the popping on decel begins to annoy. So in the middle ground I sit.

I won’t quibble with the exhaust difference, I don’t think that affects the MAJ size much (pilot and especially PAJ are what seems to count more for exhaust changes, WR to uncorked, YZ to aftermarket etc.), unless we are talking about a stock US WR vs. a US YZ (or uncorked WR). I’ve never even seen what kind of exhausts they put on these things for Canada & UK bikes.

MMMMMM.... :)

just interested in our differences and nice to get some proper feedback. i can't say there's too much anywhere on the site as riders get the E and are so ecstatic that little true information comes out.

i found the needle straight was for starting, idle and just moving off for 1-3 yards, so what's that? 3,000 revs tops?

i found the idle circuit was for low revs in second which might be nearer third gear on yours. not that you MX boys roll along and fire anywhere (fire, fire or fire!).

here you're richer than see level :D:D

must be an air pressure in the floatbowl thingy.

certainly our settings are similar higher up on the MJ and the needle given the clip change up for you and the two i would make down if i pulled the #160MAJ out.

bryan put up in his profile that he had found the altitude to NOT be a MJ problem but a PC thing. looks like he was on to something.

i'm prettyy sure a N needle would have done me and that's two sizes from Q and three from R-that's a gulf.

keep the info coming Hick.


Called the dealer today to see if the parts came in. The #45 pilot jet is here. The EJP needle is coming out of Atlanta, and won’t be here until Monday.

On the YZ timing from what I’ve read, nothings been mentioned about gasket sealer for the cover. I assume that if the cover gasket is in good shape no gasket sealer in needed?

If the carb parts are back ordered for a while, maybe I’ll tackle the YZ timing first.


The rubber gasket on the head cover is of very good quality. I did buy a spare just to have around but I bet I've had the cover off my '00 at least six or seven times and it still seals very well, and my spare languishes on my parts shelf.

Just be careful taking it apart. The half circles on the cam chain side are inserts with rubber gasket around them, that seems like the most likely area you may damage the gasket upon removal so be careful there, but I don't think you will have a problem, and you don't need any sealant. In fact that may just shorten the life of the gasket next time you remove it.

What you might want to do while you have the cams off (necessary to change timing) is take the valve buckets off (a pocket magnet works great for this) and write down the shim size (a number printed on the top of the shim that sits on top of each valve stem and under the bucket) and its location. That way you know what size you will need to order next (only avail. in .05 mm increments). So 50 or so hours down the road when you need to reshim you won't have to take off cams, then order shims, then wait for them to arrive (like any other Yamaha part they can sometimes take a few weeks to appear).

Hope this helps.

[ May 10, 2002: Message edited by: Hick ]


Thanks for the heads up on the gasket sealer and especially making a note of the shim size. Perfect time to do that.

My owners manual is getting more and more notes jotted down in it.

Almost anywhere you look in my garage, there’s a TT printout lying around. :)


After testing this weekend, do the yz timing but like chucky said get the OBELN clip #3 with 158mj you will be serprized !!!!!!!!!!!!

Hmmm, so you like my set-up...Cool :) You will have to re-jet when you go to YZ timing, I tried other needles and so far the 00 YZ needle,168mj 45pj worked best for me. I ride from sea level to aprox 6000ft with this set-up and it rips. The only hang up I have is in cold air temp (45deg.) and 4500 + ft. with Twin-Air filter, then I get an ocasional plug foul at low speed. But I don't have any problems with stock filter..Hmm?.. I went to the YZF pipe because it is both quieter and much lighter than un-corked stock. Go to the YZ board, they are allway's selling their stock pipes. Don't be fooled the stock pipe is probably the best all around pipe you can get for the type of riding we usualy do. Going rate seems to be $125-150 for new or as new.



blue beast wins :

Thanks for sharing your test results on the OBELN needle on clip #3 and the 158 main jet. Interesting combination, seem way lean. How is de-acceleration any backfiring?


I felt your setup was closest to mine, hope you don’t mind me copy cat’n you! (I’m not Japanese by the way). :D

Thanks for the tip on the exhaust! The after market pipes I’ve been looking at are 400-600 bucks! For now I’ll keep my noisy stock WR. I love that sound. My brothers is getting a KTM 520. I can’t wait to see how the WR will do! At least he won’t be able to hear his bike much over mine. :)


Way lean for an 01 but not an 02,very faint pop on hard decell.

Hey blue beast wins :

What’s your riding elevation and pilot jet settings?


0-6000 ft approx, std pilot jet, my brothers bike is the 02, no idea how many turns out each bike, temp and density is different,normal mixture adjustmant, warm it up wind the screw out, then slowly wind it in untill it starts running rough,then slowly wind it out untill it comes good and then a quater turn, should be fine.

Ok, here's my question. I am happy with the power of my 02 right now in relatively stock form. I have decided on a Pro-Circuit T-4 total system. If I run Taffy's jetting will it work? If I run Hick's jetting will it work? I know I am a pain in the ass, but I am more worried about preserving the bike than the absolute ultimate performance at every turn of the road. Don't get me wrong, I love to tinker with carb jetting. However, I would like one set of jets that I can rely on for excellent performance across the board in most conditions without EVER being lean and harm my motor! Thanks for all your help! Also, what would you guys recommend when it gets colder? All summer I will be in 70-85 degree F weather, but will the jetting specs you recommend be entirely too lean in 30-40 degree weather? I don't want to have it so lean that it will harm the engine the minute the temp drops 20 degrees.


I'm confused, you recommened an exact part number for the yz needle to me. That was for an EVP needle. You then recommend an EJP needle. What gives?


Originally posted by crotchrocket:


I'm confused, you recommened an exact part number for the yz needle to me. That was for an EVP needle. You then recommend an EJP needle. What gives?


The EJP is the stock ‘01/’02 YZ426 needle.

The PN you refer to, which I recommended to you in another post I guess, is in fact an EKP, not an EVP. That is just a typo on the Yamaha fiche, don’t worry about it. If you order the PN that is clearly labeled an EVP on the YZF fiche you will in fact get an EKP.

The EKP and EJP are very similar, with the former being ½ clip leaner. That is it.

On both my friends WRs, both ’01 models, one with uncorked stock exhaust, one with a WB R series, trimmed throttle stop, no lid, this is the jetting we run here at 4 to 5k feet, SW desert (hot and dry):

160 main

40 pilot

EKQ #3 (differs from EKP in that it is one size leaner just off pilot)


About an 80 PAJ

About 1.5 turns on the fuel/idle mix.

I don’t think the different exhausts, other than the stock corked vs. everything else, makes an appreciable jetting difference. It doesn’t seem to on the two (otherwise identical) WRs I’ve jetted, anyway.

If it were 30 degrees down here w/ any regularity I’d say the above would still be pretty close, maybe a step richer on clip and pilot.

Sorry about whatever confusion my post engendered. Hope this helps clear it up.

Called the dealer today and no needle yet. Now he says it’s coming out of a different warehouse. :)

I’m getting a little worried.

I told the parts guy I needed the EJP needle for a 2002 YZ426F. So I hope that’s what he ordered.


When the needle comes in, is there a way I can verify that it is in fact a YZ EJP? Should I bring my old DRR along and compare the two? What differences would the YZ EJP and the WR DRR needles have?

I’ll bet either he ordered the wrong one or they’ll send the wrong one. For all I know, they could be sending me a jet needle for an XR80. :D


Originally posted by tk421:


When the needle comes in, is there a way I can verify that it is in fact a YZ EJP? Should I bring my old DRR along and compare the two? What differences would the YZ EJP and the WR DRR needles have?

I’ll bet either he ordered the wrong one or they’ll send the wrong one. For all I know, they could be sending me a jet needle for an XR80. :)


It will have the code stamped on the needle right next to the last clip slot.


Is what your stock needle should say.


Is what the needle you purchased should say. If not, return to parts counter and verbally flay the bumpkin who sold you the wrong needle.

Hope this helps.



"need any help there old man?" (name that film)



Your mission Jim (should you choose to accept it) will be to help WR400/426 owners wishing to change over to YZ performance.

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