2002 WR 426 to YZ: jetting question.

My 2002 WR426 is nice but needs more power. I want to keep the stock exhaust. I’ve done most of the free mods accept the YZ timing.

Can I stick with my stock jetting after doing YZ time? Right now it starts and runs perfect.

If not, what parts do I need?

Main jet #165

Pilot jet #42

Jet Needle DQR (clip 3)


We covered this exact topic less than a week ago, didn’t we???

Get a YZ needle and then rejet your bike.

The timing changes the nature of the power, not as wheelie friendly, more abrupt, and, heck, more “two-stroke” like. Once you have dialed your jetting you can try the timing change, it is almost as easy as changing your jetting (but harder than using the search function here at TT).

Hope this helps!

Hick, I have about 53 miles on the bike now and really like it. The power is a bit deceiving it comes up, you think it’s done then ROAR!!! It comes alive! I have not seen much on TT for the 2002’s WR426’s YZ timing mod. I’m still not clear on the exact P/N’s for the needle and jets. The main jet needle required is a bit confusing to me.


Do a search on “YZ timing” and prepare to be inundated.

I do not have the PN for the YZ needle, but this should be an easy part to get, just ask for the jet needle for an ’01 or ’02 YZ 426. I am confident that you will notice an increase in power and response.

Removing the airbox lid and uncorking the exhaust are the modifications that make a WR a good candidate for a YZ needle, the camshaft timing mod can be done independently, IMO.

Hope this helps.


Thanks! I will order the needle and jets this week. Hope your right about the noticeably better part! At least I know what to set it back to.

I’d like to duplicate SoCalWr426 settings prescribed by James Dean: EKR is the stock '00YZ426 needle. Give it a try in clip #4 with the 45 pilot, 1 3/4 turns out and #172 main.

However his elevation is 4000’ mine is 890’, he has the Yzf exhaust and mine is stock unplugged WR. My question: Is the #172 going to be too rich for my setup?


At your elevation I would stay far away from the ’00 needle.

I think James Dean had/has a 400, I don’t know that he ever bought a 426. That and the altitude make a difference, otherwise I would say just listen to James the jetting master.

I think the 172 will probably be too rich. At your elevation it seems a lot of guys are one even two sizes richer (even more guys are still stock) but 172 seems excessive.

I don’t think the difference in exhausts makes an appreciable difference. I have two riding buddies, one with an E series, one with a stock uncorked, and they run identical jetting. I think both exhausts are equally unrestrictive (and loud).

I think a good starting point for you would be a 45 pilot, EJP (’01 & ’02 YZ needle) on 4th clip, and a 165 or 168 main. Your over-rev will probably also benefit slightly if you just remove the MAJ (main air jet) altogether. Really.

Hope this helps.


Thanks a million! This gives me like you say a good starting point. I’ll stop by my dealership tomorrow and order a ’02 needle and a #45 pilot jet. I’ll stick with my #165 main jet and see what happens.


hick you disappoint me. clearly the tests i've done don't mean a thing to you. i conclude that you've done your own back to back tests and come up with different results.

pull the MAJ out?

and an EJP needle?

the P needle is the sole reason for a hesitancy that can easily be overcome by revving and dumping the clutch but i tried that needle three times and at different stages of my tests. no way is the P needle as good as an M or N when moving off.

as for the MAJ i spent an entire day doing back to back tests recording the differences. the 235MAJ wasn't as good as going the other way and getting a smaller #160MAJ.

again tested. i don't remember any recorded tests just opinions to the opposite.

in the meantime there are plenty of riders that love the new low numbers.

just listen to james the jetting master!!!

you've been running a 38PJ and now you tell tk to run a 45 :):D

have i missed something here or is this what's known as a "fire in the hole" know what i'm saying?



Ok, I feel stupid again.

There were 6 different needles on the 2002 YZ fish when I ordered the EJP needle today. I wish now I would have written them down.


I just have to ask this: At 890 feet elevation, YZ timing and stock exhaust (unplugged): with lets say an 2002 YZ M needle, what would you go with for main air jet, and pilot air jet?


why change anything?

if the bikes are spot on for sea level you'll find they run slightly rich at altitude but the jetting will be within the range of normal riding. put it this way; the bike you're riding now is richer than the bike you'll have. so ifit ain't too bad at altitude now it's going to be excellent after isn't it!


My lousy .02 cents:

Im running a 168 main at or about sea-level, but usually up to 900 or so feet. That with the ELN, makes a very noticeable improvement from stock.


Assuming then your write (and to me it makes some sense), and my goal is more power and less bucks, then: I’ll change only to a YZ needle and leave everything else alone.

The settings in my Signature were copied from a TT member helped by James Dean. They work well.


(and from here I need some help)


If I go your way and not change anything,

I still should go from a 42 to a 45 pilot so the pilot screw is not turned out so far. Right now it’s 3 turns out and rather loose.

Soooooooooooooooo, how does a ??? YZ needle in clip#? and a #45 pilot with one turn out sound?

Can anyone help?


Originally posted by Taffy:

hick you disappoint me.

I would be worried Taffy, but nobody can satisfy you.

The thing you continually fail to account for or otherwise ignore is elevation. But then, the UK is pretty flat ain’t it.

I run a 38 pilot when riding over 6k ft. of elevation. Currently I am running a 40 pilot at 4 to 5k ft. of elevation in summer temp.s.

Also, you have a 400 and we are talking about a 426. I don’t know that this is a significant difference, but stock jetting on a 400 is markedly different than that delivered with a 426.

I’m not saying I am as worthy a tuner as you, but I’ve tried a 180 MAJ and 158 main (independently and together) after following one of your posts, and have also tried to ride my bike at my “home” altitude with leftover 8k ft jetting (38, EKR # 2, 158) and it was very obviously too lean on the clip position, less so on the pilot and straight diameter. The main and MAJ I set separately by making a high speed pass down a runway, and my rear end tells me a 160 w/ no MAJ works well.

Are you saying P is too lean on the needle diameter? For me this is decidedly not the case. I haven’t tried anything richer than a P diameter needle because the P itself is too rich, that is why I run an EKQ.

And for God’s sake don’t get on my case for supposedly switching horses down the stretch, you went from one extreme to the other, at various times brow-beating the denizens here to follow your improvements.

I would never ignore your advice, I in fact have followed your progression w/ your 400 and have experienced many of the same benefits, but not always and not always to the same extent (accelerator pump mod.s are a good example of this).


Where did you find an ’02 fiche? If you ordered from a mildly competent parts guy and asked for the stock ’02 you should be okay. It should have the letters OBEJP stamped on it just below the clip grooves.

To answer you question I think starting in clip pos. # 4 with a 45 pilot should be very close, stock YZ is EJP-4 and a 42 pilot.

Hope this helps.


When I ordered the parts this morning, I was looking along with the parts guy at the ’02 fiche. We were looking at the carb. There were at least six different needles, I went stock EJP.

The 45 pilot jet and EJP needle should be here Friday. Don’t know when I’ll have time to install them. Should be able to do that part first and verify things are ok before the YZ timing mod (one change at a time to aid in trouble shooting).

I’ve had the carb off three times and the needle out twice and it seems like there were some letters stamped on the needle. Not sure what though.



in other words

silencer (-10), sea level(+10), 160 MAJ (-10)



open pipe (+10), altitude (-10), 200MAJ (+10)


so our MJ's are the same on average.

my needle was on clip 2 for me to be the equivelant it would have to be on clip 1 but it was on 5!

that's 4 richer so no wonder you were running lean. altitude or not 4 clips was a lot of difference. BTW the last tests that brought the MJ down to 150MJ saw the needle rise 2 clips so previous to that we would have been 1 clip apart and so by lifting your needle THEY WOULD HAVE BEEN THE SAME bar my MAJ change (worth as said two clips at that time of testing).

as for the needle straight, you're clearly leaner here though. an M with a 35/50 and you with a Q and a 38/?.

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?


wayneo426 :

Thanks much! Your input helps me sort this out. Street legal would be a blast.The bike sits kinda high though, bet it’s bitch on a windy day buzzing down a freeway. Nice part you could just ride to the trail and wouldn’t have to haul it.

What are some of you other ’02 WR426 guys at sea level with YZ timing, and stock exhaust unplugged running for jetting??????????????????????????????????????????????????????

Hi TK,

I went the same route as Wayneo426 with my 01 wr426: OBELN, 168, 48 pilot(3/4 turn out) 200 Maj. YZ timing, BK, Grey Wire. I did lower the needle to the #3 position after a few rides and now have WR that runs great at all rpm's!

James Dean is the the jetting guru!! ThankYou

I ride ground to about 1500ft



I run the stock exhaust(plug and lid removed)

Up here in Washington State it's mainly a 1st & 2nd gear affair. lots of tight, rocky, rooty trails. I would guess that a YZ needle would be great for more open terrain, but for up here, low end grunt is where it's at for me. My next purchase will be a heavier flywheel weight.



Thank you for sharing your settings. 1500ft is close to my elevation.

I know that the pilot circuit and the main jet circuit overlap each other, and that the needle affects the main jet circuit. So, what symptoms would the bike give that would require a clip position change?




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