Hey Taffy, Michael Rundle, Indy, others, quick question for you?

Well, first thanks to you guys for the great information and posts on Jetting. The archives are a great wealth of information. My WR426F was so rich when I bought it, it was really a shame. I have it close now, thanks to you guys, see my sig.. However, I want to go to the next level. Taffy, I am going to the Yamaha dealer today and buying the exact same jets and needle as you. I have 2 questions.

1. Since my bike is a '02 WR426F without BK mod, etc..., is the jetting still the same as your bike? Are the carbs the same? If not, what should I change

2. I ride at Hungry Valley, California. Same temp. as Australia and roughly between 3K - 5.5K feet. Should I change the setup in your sig. to accommodate or not. Please give me your recommendations.

Thanks in advance for all your help. It was so much easier to jet my old bike, a XR650L. Anyway, the WR is a way better and more fun bike. :)

before i read your signature i said to myself that the EKN or EKP would do. if you're running EKP you'll be fine. hick is always on about a Q needle the '00 yam YZ was EKQ i think.

your pilot jet could keep coming down with the correct PA to go with it. you must do your BK mod soon although i believe either last years or this years comes pre set. check this.

that's it really. the main difference is the MJ. here though i can't tell you because nobody has ever done any proper testing. they're too busy riding but really, you'd have thought SOMEBODY would have done it!

if i run a 150MJ/160MAJ at sea level w/ silent pipe and an open pipe is worth a 155MJ then at altitude i would have thought jetting in the 140's wasn't out the way.

without the 160MAJ it would have been about 155/158MJ for me and down to 152MJ at your height i would have guessed.

i also never experimented with plug range. i think there was loads of testing left.

so try the 160MAJ and the MJ on 150 and take the PJ down to 35 or 38 with a PAS.


Taffy, Thanks for the feedback. So, since I am running the stock MAJ (which I guess is a 200?), then you are saying get a 160 MAJ and reduce the MJ to a 150. What do you think about the needle in the 3rd position? It came in the 5th position and the bike would stumble at 1/4 throttle. I set it to 3rd position, but, have not been out to do testing. Now, when I start the bike cold with the choke on, it idles very high. When I take the choke off, it idles normal. This seems correct, right? Before it was so rich, I could not use the choke without flooding it. I have a 38 PJ at home. I guess I will try that. What is the stock PAS? What PAS should I buy for a 38? I do not really understand this PAS screw thing. I read something about that and sudco.

Stock '00 needle was EKR BTW, a big "oops" for Yamaha that year...

The '02 doesn't need the BK as bad as prior years, but it can still benefit IMO. It sure won't hurt anything...

Ditch the 42 pilot for a 40. At least. You can skip to a 38 right off, but it is probably a better idea to go one step at a time.

Stock PAJ is 100. A 75 may work for a 38, my 426 like about an 85 w/ a 40 pilot. Get the adjustable PAS from Sudco, it replaces the fixed-size jet w/ a screw, so no more buying Pilot Air Jets.

(800) 998-3529

Spring PN: 021-235

Screw PN: 021-230

One turn out on this screw is equivalent to a 100 PAJ, 3/4 out is about a 75 I think. Somebody posted a chart recently showing all the sizes and corresponding turns out...

150 MAJ seems small. Again, IMO you are better served going in increments, and a 158 may be enough.

Stock MAJ is a 200.

I think that needle is good, second or third clip. Anything richer I would guess will not work as well.

Anyway, if you went:

EKP # 3

158 w/ 180 MAJ

40 w/ 85 PAS

I think you would be very happy, but that isn't to say you can't go even leaner as Taffy is suggesting. Try it and report back to the unwashed masses...

As for the choke, mine did not work at all ('00 and '01 YZ at 4,000 ft.) until I went to a smaller choke jet. Unfortunately, I can't remember which size, may have been 62 or 65, but the stocker was too large for me.

Hope this helps.

one thing you learn with me that i don't know any part numbers, i don't know one year needle from another! i always used to have JD to mother me and recently when i wanted a needle for the husey i went to hick and he came up with it. so tonight, for one night only i bring you;

the YZ426 needle for '00 was EKQ and part # 5jg-14916-e1-00.

hick is spot on and he is simply saying that here is a conservative step forward for you to try i'll leave that to you but i'd be lying if i said i didn't feel confident.

the reason you now need a bit of choke is because you have shoved the needle 3mm further into the hole blocking it at tickover/when the bike starts.

everything about choke tells you about your bike. i've said it time after time after time.

you haven't run the bike after the needle change yet you want our life stories.... :)

i once helped a bloke like yourself, he changed everything said it was ok except for starting. i asked him to explain the engine on choke and it was all too much for him, he couldn't cope :D :D he'd become a 'tester' and it had all become too much for him :D.

just like jetting Qs you should do everything else before you set the choke jet and although i did the APJ last that would be for you. me? i took the thing off for 12 months. have faith.

BTW hick got his MAJ and MJ mistaken and it's a 158MJ he recommends and the 150MJ seems small.


OK, Guys, I ordered the following through Sudco, which by the way is about $3 cheaper per jet than the Yamaha Dealer and close by me.

Adjustable Pilot Air Jet

158 MJ

180 MAJ

40 PJ

150 MJ

160 MAJ

35 PJ

I will try these 2 combinations and see which one is better. BTW, so far, I have been able to change the needle, pilot jet & main jet without removing the carb. You just loosen the accelerator cable bracket and associated carb. clamps and rotate it. Do I have to remove the carb. to replace the PAJ and MAJ?

Anyway, I should get the parts by Monday. I am on travel for work next week, so, I will not be able to test the new parts until next weekend or the following weekend. I will let you know how it turns out. For this weekend, I will use my exisitng jetting.

Thanks for your help. The people on this board are very helpful :)

While you are at it you might as well get the 38 PJ as well as the EKN, EKP, EKQ needles. to give you a complete range of adjustments. :)

Indy, This may be a stupid question, but I noticed in another post that you stated you are running the YZ NDJN needle. Your signature calls it an EKP. For some reason I am just not getting the conversion between the two part numbers. Can you help me out? :) Also, is the NDJN leaner than the standard NCVQ?




I already have the 38 PJ. I think I am going to stay with the EKP needle that is installed currently in the bike. I am not sure I can gain more acceleration by changing needles. I want the most agressive needle I can make run clean with the right jets. The EKP seems aggressive enough.

I have them all. I am testing the different needles with pilots to get my jetting spot on. So whenever you see my signature it will be what I am currently running ( I dont see how everyone leaves their jetting the same throughout the year). This is my first Thumper and I am learning a lot and trying all the recommended needles and settings on this forum. One thing I have noticed is that the pipe flow and design has a big effect on the pilot circuit set up for my bike. I know Taffy and Kaze are at different ends of the spectrum when it comes to pilot choices. I am going by my results and coming up with my own conclusions. I am not advocating that I have the perfect jetting but I expect to have tried everything on this forum the end of the year. You dont need to go to the extents that some are going to get jetting where you like it. Taffy can write a book on it. James Dean has. Kaze, Hick, EGO and LarryCO have some insightful experience but dont expect your jetting to be plug and play from anyones recommendations. :)

So tonight, for one night only i bring you;

the YZ426 needle for '00 was EKQ and part # 5jg-14916-e1-00.

Hmmm. My '00 came with an EKR, which I replaced first with and EKP based on advice from JD, then I later split the difference with an EKQ.

BTW hick got his MAJ and MJ mistaken and it's a 158MJ he recommends and the 150MJ seems small.



One thing I have noticed is that the pipe flow and design has a big effect on the pilot circuit set up for my bike.

I noticed the same thing with the WR/YZ 426. I still think a lot of folks are thumper neophytes around here, and are used to buying an FMF gnarly for their two stroke and changing the main jet and maybe the needle; how many "what jetting to run with an XYZ pipe" posts do you see?

IMO changing a two stroke pipe design is more akin to changing the cam in a thumper. From a jetting perspective changing a pipe in a thumper is like changing the air box, and that is why I think I'm seeing different jetting from WR to YZ in the 450 on this board that I never saw with the 426, here or personally. Just an observation/theory.

I am going by my results and coming up with my own conclusions.

Please let us all know what you come up with.

Kaze, Hick, EGO and LarryCO have some insightful experience but dont expect your jetting to be plug and play from anyones recommendations. :)

Ditto that.


What PJ comes stock ? I don't even remember what they put in for "extras" I think I need to lean my PJ to get rid of the Bog off Idle Snap. IF the RPM's aren't up the bike bogs. Looks like the 29th for a ride :):D :D :D :D

Taffy or Anyone, I could use some help. I have a 98WR400 and recently changed to the YZ timing. The bike ran great before I changed. At that point, I had the airbox off, baffle out, 13 tooth front sprocket, the carb was stock, Norhtern Michigan 500-1000ft. After I changed the bike was running hot and back firing on decel. I then changed the main from 168 to 172 and dropped the needle to pos 4 from 3. The bike now runs great in 3-5, but 1st and 2nd are way too short, idle is all the way out. My thought is to go to the stock YZ settings on the carb and sproket, but I was looking for a little help

i don't get what you mean by 1 + 2 are way too short? try it by me again.

it's not a big deal that the bike runs a bit hotter, it should now also be running BETTER! 13T is too small IMHO if you get this running right.

but you will need to modify your jetting considerably. as it's a '98 i would find out if anyone else has changed anything and take nothing for granted. so you're going to have to strip the carb and write down all the settings. give it a good clean while you're there.

a bit of popping is unnerving at the beginning but post your settings up here and we'll try and help.


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