Jettings & Setting.

I have a 00'WR (european model) and i'm thinking of replacing the exhaust with a FMF powercore 4. What jetting is required, is it only the main jet that needs replacing and if so what size would you guys recommend for these UK shores. Is there any other settings I will need to play with. Thanks for your help in advance.


Go to the Technical Section. There you will find different jet specs the guys are using.

Is your restictive airbox lid removed?

If you haven't done it yet (maybe it's not on the Euro model?) the throttle linkage restrictor should be properly shortened to give you full throttle capability.


99 WR, all YZ mods, de-octopused, OEM YZ tank and seat, jetting by Clark.

Moab bound for 2000!!


The jetting listed in the Technical section applies to your euroean model but the needle isn't listed. The code OBDRQ is very close to an OBDVP except it is 2 clips richer. DRQ #3 clip position is close to DVP #5. Clip #2 or #3 should work good.

I've been looking on the technical page and have one question to ask, what needle is the DTM because theres nothing close in the service manual, they go from DRV to DRP. I hope this ain't a stupid question. :)

Difficult question with a tricky answer. The manual doesn't tell you what the other model years were using. DTM was used in the '98-'99WR's.


Needles have 3 components - diameter, clip, and taper... and codes have 3 letters for just that reason.


The needle codes work as follows:

-First letter is taper- D stands for .75 degrees, E is 1.0 degrees and is used in the YZ426

-Second letter is the clip range(height) relative to mid taper. R,T,V are one clip each apart. The DTM is runs exactly the same as the DRM only it is 1 clip leaner. DTM#4 equals DRM#3. DRQ#3 equals DVQ#5.

-Third letter is straight diameter. M,N,P,Q,R,S are each .01 mm bigger from rich to lean.

-notice in your manual that DRM is the richest needle listed, which agrees with Clark's evaluation of the DTM.


-Last letter is for low throttle settings 0-1/4 and transition from idle.

-Middle letter is same as clip position and controls 1/4 to 1/2 throttle.

-First letter is for balancing the transition between 1/4 and 3/4 throttle and is used with the middle letter to focus jetting changes close to 3/4 throttle and transition to the main jet.


Did that answer the question? :)

(more than you ever wanted to know!!!)

James Dean

[This message has been edited by James Dean (edited 06-14-2000).]

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