Baseline jetting

Go figure, more jeting dialogue!

After reading all the threads for months and seeing activities like drilling out ET's, gray wires, BK mods, EK* needles and OBELN needles, I'm in need of therapy!

Anyway, it looks like it might cool off here this year (finally!) and I'll have some time on my hands to tinker so I thought perhaps I could con someone into summarizing all the experimentation for my application:

99 WR400

modified throttle stop, FMF Power Core IV (stock header)

That's it (engine wise). Still has WR cam timing, octopus, etc.

Elevation: Approx 300' (Maybe up to 1500' if I go out of state).

What are the latest recommended baseline jetting specs, along with mods done using those settings? (YZ timing, gray wire disconnected, etc.)

And would anyone (JD? :)) take it upon themselves to make a summary table of this info and post it in the Technical section so that dweebs like myself won't continue to ask what needle, MJ, etc., should I start with?

Thanks guys and keep up the good work!

YYYYAAAA what he said.

99 WR400

Stock pipe uncorked, air box lid removed, throttle stop cut. NEXT YZ timing and Depuss.




check out (moderator) Bill's signature. I believe he has his jetting specs listed.

His 99 smokes my 99.


'99 WZ/YR (you choose!) with ALL YZ mods, de-octopused, DSP Doug Henry airbox w/ velocity stack, FMF PowerBomb header, Stroker SX-1 silencer, SS front brake line, OEM YZ tank, IMS YZ seat.

Thanks Kev and thanks to James Dean, Clark Mason and all those who worked so hard on jetting specs.

Here's the jetting for a deoct, YZ timed 99 that does start perfect and rips. Now if I could just ride better :)



99 WR400f, YZ timed, MX-Tech suspension, Scotts steering damper, White Bros E-Series (12 discs), tapered header and a/f. Kouba T-handle for the fuel screw. Works Connection billet throttle tube and frame guards. Cycra Pro-Bend, triple clamp mount handguards. Thumper Racing rad guards, Renthal Jimmy Button highs, YZ Tank and IMS seat, YZ number plate, odo removed, de-octopussed (Thanks Clark) EKP #4, 50PJ, 175MJ, 100PAJ and 65 SJ at 500-1000' Thanks James Dean!


Ok .... looks like I will go to YZ tilling and depuss my WR at the same time. Also, I took your advise and bought the Jimmy Button highs, and what a difference( thanks for that ), alot more room. I think I will even add some risers also. Like I said before I'm new to dirt bike riding and thumper talk, so all the advise has been a big help. People have even given me there home phone numbers for assistance when I do my YZ timing mod -- I can't say thanks enough to some of the members of this forum.

Pete :):D :D

Also, do you have a part #for the EKP.


Sorry can't help with the needle part #. Like you said, there are some great people here, like Ken in NH. Who gave me the needle last June when he came down to ride.

I did but the vacum caps at AutoZone. They had them in Yamaha Blue :)


Originally posted by WRFUN: you have a part #for the EKP.



Thanks anyway. I just want to order the right stuff, and do this one time. I will keep searching. I noticed different part #'s listed all over the forum so I'm a little hesitant about ordering yet. Also, can any needle be put in any year bike or is the needle year specific? Is there a EKN for a 99 and another for 00 and so on....


Pete :)


Thanks for your input, that matches most what I found.

Pete :)


One problem you may encounter is that the PN I listed may be described, incorrectly, as an EVP on some (or all) parts fiche diagrams. Don’t worry, I have ordered this needle over the phone (NCY), I covered my ears when the parts guy on the other end said “EVP,” what I got was an EKP.

The needles will go in any year WR/YZ, as a matter of fact they will also go in the 250F which has the same carb in a smaller size. I know that some of the optional needles listed for the 250F have been recommended as alternatives by JD on this board, so if the EKP is on backorder for whatever reason there are several other options, including aftermarket (non-Yamaha) sources.

If you have trouble post another topic.

Hope this helps.

[This message has been edited by Hick (edited September 10, 2001).]


Thanks for your input. I will let you know.



Thanks for the info. I've been understandably distracted the last couple of days, so please forgive my delay in expressing my appreciation.

I'll be out of state working for a while, but hopefully I will have a chance to make these mods soon.

If I have any issues as I go,I hope you don't mind if I direct questions your way.





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