I tried to order the yz needle from my dealer they said its on backorder and wont even ship til the end of the month. I was hoping to do all my mods before then. Will be ok doing the airbox lid, yz timing and white bros E series with the wr needle. I am worried about being too lean with the air box lid off right now I have a 165 main, 42 pilot, middle clip on stock needle, DRR. they gave me a 38 pilot, and 160 and 170 mains. I ride in northern california about 300 ft above sea level. Any ideas on which jets I should be using for this setup. I want a safe baseline to start from and then Ill mess with it from there.

Which needle is on backorder? It is a shame to wait 2+ weeks for a needle, perhaps there is a substitute from the '00 parts fiche that will work.

I don't own a WR, but I know that the needle is the principle jetting difference between the YZ and WR. BTW you may consider changing your pilot air jet to the YZ part as well, size # 100 vs. # 75 in your WR, esp. if you go with a bigger pilot, which segues nicely into my next question:

Who gave you the 38 pilot? That seems awful small, especially for your elevation. That is what I run in my '01 YZ above 8k ft., I would think most guys down there have a 45 or even 48 :)

Anyway the restricted air box, exhaust and different timing are the only other significant engine differences, so I would say that changing all that without swapping the needle may not work too well. I don't think it would be so lean as to damage you motor but I guess that depends upon the conditions.

Hope this helps.

It was the EJP needle thats on backorder. I went in today to try and get the EKP needle but they didnt have a part # for it.

Ive heard a little about the pilot air jet, but wasnt sure if I should go up.

I have a 38 pilot in the bag they gave me with the owners manual. Theres a 42 in the carb right now.

I ordered some jets today a 45 pilot, 168 and 172 mains and an EJR needle whatever that is.

I dont know when any of these will get here. Im thinking Ill do the mods, put in the 170 main and hopefull the 45 pilot if it shows up soon. Ill raise the needle one or maybe 2 cilps. What do ya think?

Here is the PN for the EKP:


(it is on the ’00 YZ fiche as an optional needle)

Here is the PN for the # 100 (YZ) pilot air:


The EJR you got is two sizes leaner on the straight portion compared to the EJP (the last letter denotes the straight diam.), this governs mixture at smaller throttle openings (say 1/8th and below) and sort of overlaps with what the pilot is doing.

The ’00 YZ came with an “R” needle (EKR) and it was too lean off the bottom, even for me at 4k ft. (and hot). It worked well at high(er) altitudes though in my ‘01. A bigger pilot and 2 turns on the fuel screw may help compensate for the leaner initial jetting. You may get to experience the “’00 YZF bog” that we all know and love as a result of the lean spot.

I guess a few rides won’t kill you, but definitely try the EKP or EJP as soon as you can.

Having said that, I imagine the EJR is a better option than the DRR. Hopefully someone who rides at your elevation, on your bike, and who knows what is what will happen along eventually. For now I’ll take a stab at it and recommend you try the 45 pilot, 168 main, and the EJR on the 4th clip to start out. With the 45 main I think you should also be running the larger pilot air jet. If you are stuck, for now, with the stock needle I think dropping the clip one is worth trying.

Having the right needle in the FCR is really what jetting these bikes is all about, IMO.

Hope this helps.

Thanks for the info. Does anyone know a good online supplier for OEM yamaha parts? Im sick of my local dealer. I spend 500 bucks and they still give me crap for not buying the bike there. Even though when I bought my bike they couldnt get one til 02s came out

they also have a microphish online.

free shipping after 50 bucks.

they will match some prices if they can.

I just bought 3 s-12 tires for 190 bucks


The YZ250F needle is equivalent to the EJP also, adjusted by another clip position.

EJP#3 clip position = ELP#4 clip position

EJP#4 = ELP#5

OBELP - PN 5NL-14916-EP

For some unexplained reason it is cheaper than the other needles ($7.76) shown online at

Be careful with Parts Fish (, last time I checked they only had one PN listed for the ’01 YZ needle, and it was not the std. needle (EJP) but an optional one (I forget which).


I did not realize that you had high altitude jetting experience with the '01 yz426.

Will you please share your specs for ~7000ft? Including acc pump, needle & position, PAJ, etc.

I am currently at 162 main, EJP/clip #3, #38 pilot 1/2-3/4 out, PAJ #100, acc pump duration ~.25 seconds.

It runs very well, but there is room for improvement off the bottom. I think I will try richer on the needle clip next.

QUESTION: Do you think I should try a #75 PAJ?



Rick Fuller

'01 yz426

'00 yz426 destroyed by fire in desert race 4/22/01

'81 490 Maico


I have ridden my bike twice at about 8k and above. Once for 3 full days at Rampart Range in CO, and once in the Sacramentos in So. NM for one day. I ran the same jetting both times:

The main doesn’t seem to change much but I did run a 160.

38 pilot

1.25 out

Adjustable PAJ at around 80 or 90 (hard to tell exactly)

EKQ #3 (Up in CO I was tempted to try #2 but this was okay).

The EKQ is a needle I had tried in my ’00 (Yamaha PN: 5JG-14916-E1), it is one size leaner off the bottom, and a half clip leaner on the clip position. I think you should try it. That or the PAJ might be that last 5% you are looking for, the #75 PAJ may work better than the #100 with the 38 pilot. Or you can take the route I did, get an adjustable PAJ and split the diff (Sudco, 800-998-3529, has the adjustable PAJ, you need two PNs, the spring and screw, together around $15 but worth it IMO).

When you consider the half clip thing (think of my EKQ #3 as EJQ #2.5) # 2 may be worth trying on your EJP. So I don’t think you need to be richer on the clip, at 4k where I usually ride I use EJP #3, I tried #4 and it was obviously too rich.

BTW when I go back down to 4k ft (but it is pretty hot down here right now) I change to:

40 pilot

EJP #3

Everything else I leave the same. I should mention that I have one of those huge FMF Q silencers, that may have richened things up (requiring leaner jetting) a half size here and there.

Hope this helps.

I forgot to mention, I left my acc. pump the same, I've never timed it but I'm somewhere in the neighborhood of 1 mm of total pump stroke (measured at the rod).


I just found this & glanced over it. It looks awsome! I will read it later & get back to you. I am Stoked!!! (& tipsy)



Rick Fuller

'01 yz426

'00 yz426 destroyed by fire in desert race 4/22/01

'81 490 Maico


I tried the EJQ #3 yesterday and it seemed better. Today I will try the EJR #3 first, then either the EJQ or EJR #2.

I'll keep you posted.

BTW Before this post I tried EJP #4, and it was definately worse.


Rick Fuller

'01 yz426

'00 yz426 destroyed by fire in desert race 4/22/01

'81 490 Maico

Well, so far this is the best it has been.

Pilot: #38 @ 1 1/2 out

Needle: EJR clip #2

Main: #162

Acc. Pump Duration: One full turn out from .3 seconds

I made the last adjustment to the acc. pump on the trail, so I was not able to time it.

I am not the best tester, but I can't tell you how many corners I overshot on yesterdays ride. I have a 30 mile loop out my back door that I do 3-5 times a week, and I know every inch very well. Coming out of several corners I found myself panic braking to make the next turn. The same ammount of throttle for the same ammount of time (as yesterday) resulted in much more acceleration.

Once or twice I wicked it wide open instantly from a very low rpm. This resulted in a pop through the carb, then instant acceleration. That is when I added the extra turn out (more fuel) on the acc. pump. That seems to have cured the pop, but I did not really test it thoroughly.

I feel I still need to do a bit more fine tuning, but now it truly is awsome.

Important notes; all testing done at 7-8000ft, '01 yz426 with Big Gun SDS (single,dual,single) pipe. Big gun claims this pipe makes 1 full HP more than thier others at the bottom.


Rick Fuller

'01 yz426

'00 yz426 destroyed by fire in desert race 4/22/01

'81 490 Maico

I hope you "WR" guys don't mind me finishing this out on "your" side. I just picked up on some info from Hick, and so far it is the icing on the cake as far as jetting goes. I had almost given up on further improvement until Hick's advice/experience. I find it difficult to tell subtle differences in throttle response, but with Hick's info I was convinced to go leaner. In my case leaner is where the power lives!

Thanks to all


Rick Fuller

'01 yz426

'00 yz426 destroyed by fire in desert race 4/22/01

'81 490 Maico


Thanks for sharing the settings you came up with. This post did not go unnoticed and should be very worthwhile for others riding at your altitude looking to get the most from their jetting. This should be regardless of the pump timing.

What ricky has done is increased the needle straight diameter(EJP to EJR) and shifted the clip position(#2) to lean out the entire range. This is despite using the RICHER needle taper that comes in the YZ426.

Anyone looking for big gains in performance on a WR at high altitudes should take note of ricky1's and Hick's jetting. This will be the biggest gains for your $dollars$ you will find.


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