First, a big thanks to JD, Clark, and Taffy for helping us to understand how to jet these bikes! I thought I would post my setup as it seems to work fantastic. Perhaps others can benefit from this too. There are A LOT! of new folks on the list that may want to listen.

I'll preface this by saying I have tried quite a few settings before, my jet parts counter guy links I'm a loon. This has been a learning process for the last year. While other settings have given good results, the following has given the best so far in terms of sheer power that is still useable.

Temp: 50 F

Altitude: 800 ft

Humidity: 48% (could be a little off, this was from a very old baromter)

Terrain: mixture of mud, soft MX track, leaf filled trails, hills, no sand.

Bike: '00 WR400. YZ timed. Stock YZ pipe. WB tapered Ti header. Airbox lid off/thottle stop cut, WB powerfilter. No other engine performance mods. Other stuff than may be of interest: Use castrol 20W/50 oil. Red Line watter wetter.

OK, here's the beef:


Needle: EKP #4

Main: 170 (172 felt no different)

Pilot Jet: 48

Fuel Screw-1.1 turns

Main air jet: #100

All other jets/settings stock (AP and TPS stock)

As a few folks have mentioned, a combo like this gives a nice torquey feel down low and is smooth on the trail. The moment you wick it past 1/4 thottle, it leaps to life. 4th gear wheelies (14/52 gearing) where doable for sure. Very smooth, yet on the verge of peaky power. Slamming the throttle open is not a problem, it doesn't bog at all!

I was using the EKN for a while, and while it felt pretty darn good, it seemed to "overreact" a little too much. Wheelspin seemed to be more of an issue than the EKN.

Since it's a typical slippery spring, I opted to continue to use a little smoother combo. Thre EKN (#4 was really the only position that worked well at all) also seemed to bog a bit when opening the throttle quickly from idle/off-idle.

I hope this helps someone out with a '00 and similar setup. Please note, with WR timing this probably isn't the hot ticket.

On a totally separate note: Under the advice a tire thread a few months back, I tried the Mich S12 front/D755 rear for soft-terrain conditions. The D755 works better than a 756! The S12 was AWESOME! The control and resistance to washing out was superb! I may keep experimenting with rears, but the S12 is a keeper!


Thanks for taking the time to share this with everyone. Glad it's working for you too!


No, Thank YOU James. I and countless others probably wouldn't have tried such radically different settings it you didn't give us the facts to let us make an educated decision.

Sadly, though as the temps/humidity rise to 80+/70%+ the settings may need further leaning for optimal performance, but hopefully not by much.

I may be interested in experimenting with one your trick triple tapers, too. After trying countless combinations of needles/clips/jets,

this is something I have been wondering about. Hook me up!

BTW, Jay R from Cinci says hi (rode with him two weeks ago)-he sold the WR and has a KTM250mxc

I'm also having some good success with my EKP in the #4 clip position. Still using the 165 MJ and 45 PJ at about 1.75 turns out, WR timing. Haven't had time to look at the plug after last weekend in the high desert, I suspect it's still a little lean. Could hardly keep the front end down above 1/2 throttle from midrange to top-end! The power delivery is still a little upredictable in that range, will post later with more info.

I would also like to thank everyone on the jetting issues. I finally got my jets last week and got my bike back together and went for a ride sunday

I must say it has never ran better. From start all the way up to WFO it runs 100% better. The power is awesome and on the pavement, 1/4 throttle in 2nd gear sends the front end to the sky!!

I went from totally stock jetting, stock pipe, yz timing and stock wr tank and seat to

pro circuit pipe, yz tank and seat, and EKP #3 #100 Pilot air, #48 pilot and #170 main jet.

Needless to say it was a totally different bike. It was like I was riding a dirt bike again instad of a couch. Power is unreal and I can actually carve turns now.

I didn't get a lot of riding in due to a very bad wreck at the riding spot- yamaha banshee vs. honda xr50-70 head-on. The kid on the xr was very bad off so we took time off from riding to check out what was goin on. It took about 15 min. to get a helicopter in but they kept him in the ambulance for about 15-25 minutes after the chopper got in and I overheard someone say later that he had passed. I kinda shrugged off that scenario but seeing how long they kept him in the ambulance after the chopper got there I thought about it some more. Usually when the chopper gets there they are gone in a few minutes. I remember seeing them put him in the bird but I was so far away all I could see was a sheet. Maybe his injuries were fatal. What a sad day. I wonder what his name was? Sorry to bring it up but I get aggrevated when some cowboy with little or no riding experience goes wide open without regard to his or other peoples safety. I don't know all the facts but normally where we ride I see all kinds of idiots flyin around on 4-wheelers, no helmet or any other gear or riding experience.

I guess we just have to keep an eye out like usual.

Sorry to get off the subject, just had to get it off my chest. Thanks everyone!!


The Michelin S-12 and the Michelin Enduro Competition III are esentially identical tires except the Comp III is a DOT tire and it also works and sticks great. So I you need a good DOT tire for the dirt its probably the best you will find.


Anyone have an idea where I can get an EKP needle fast? My dealer says that they are not available and they have to do some "research" to try and get one.


The parts fiche for the '00YZ426 is mis-labeled and it always confuses them. The parts fiche says EVP incorrectly.

Yamaha part #5JG-14916-EP is EKP (as shown in the '00 YZ426 shop manual)

If you want another option Sudco at 1-800-998-3529 sells an EMP needle that is brass. Use 1 clip position lower to get the same results, EMP#5 = EKP#4.


[This message has been edited by James Dean (edited 03-16-2001).]

One thing to mention.. I Just bought a 2001 Wr426... and Using Standard Motor oil is a Serious NO NO!.. It will mess up your clutch, and doesnt have the special additives that 4 stroke Motorcycle Engines can Use since they Dont have a Catylytic converter, and various other emmission controls. Castrol is a Fine oil for your car.. but Not For your Scoot.


I know its off topic.. but I just had to mention..

I've been using Castrol GTX 10w-30, since day one in my 99? No problems yet! :)



86TT225, 99WR, WR timing, throttle stop trimmed, air box lid removed, White Bros head pipe, silencer and air filter. De-octopussed. Works frame guards and Thumper Rad Guards, Scotts steering damper. Odometer and headlight removed. Moose hand and mud guards. YZ stock tank, IMS seat and number plate. Renthal Jimmy Button "highs" and Renthal Soft half waffle grips. AMA, SETRA, Happy Ramblers MXC.

They say that Standard Motoroil has an Agent in it to cause what they call Friction modification. Its all well and good for the Engine portion of the bike.. but not the clutch.. How much has your clutch been truly slipping?... Its hard to know. But I understand it can be more serious than it appears. You might talk to your local shop and get another opinion. Ive asked around here over the Years, and Ive heard about this before. Appearantly, the slippery formula of the Oil causes the Clutch plates to have trouble "locking" to the Basket. And that causes slipping.. The bad thing is.. If its accelerating slipping.. its also accelerating wear. Just like a Dry Clutch in a car.. only slower. Thought Id throw in another couple cents to help you out. :)

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