E Needle results HELP?

The snow is all gone and its 50F. 1000' to 3000'

99 WR with WR timing

Pro Circuit T4 exhaust with quiet core (not so quiet).

EKN #4





Fuel Screw 2 turns out.

RESULTS: way rich closte do 1/8 to 1/4 had a lot of lag until I opened up past 1/4 throttle.


PJ45 MAJ75

Fuel Screw 1 1/2

Tried Fuel Screw from 1/2 to 2 Turns

Lag and then stumble between closed to 1/4 throttle almost like it was fouling.

Plug black and sooty.


PJ45 PAJ100

Just a little lag at closed to about 1/8 throttle but showed signs af just a litle lean.

Never changed the needle or clip potision or MJ.

Seems to run great once I get above 1/4 throttle.

What should I try?

PJ42 with PAJ100?

PJ with PAJ75?

Change clip position?

Ran pretty good with:





Just a little lag between closed to 1/8

I have an '01 WR 426, don't know if your's is the same or a 400, after reading jetting q's there seems to be a difference in the jetting. the settings below were perfect everywhere except wot near the rev limiter, it got just a little rich on the highest grade pump fuel. Now I am running a 25/75 mix of VP C-12 and the highest grade of pump fuel I can buy (92-93) and It's perfect.

Get a little screw driver bit and tweek that fuel screw while it's running, then ride it, tweek, ride, tweek, ride. Can you turn the fuel screw All the way in and the bikes still runs? Then go to the 42! There is NO magic setting 1/2 increments of the fuel screw, just tweek it and see how it feels by the seat of your pants. Do the little snap wheelies and see how it responds. All you're worried about with the pilot is just getting a good idle and snappy punch right from just off idle. THEN, move your needle if you are encountering a stumble or sputter when pulling into the mid-range.

The carbs are different than what Bigfoot & I have.

Forget plug color at this point, you're nowhere close to being "dangerously lean". The FCR just has to be ridden or dyno'ed to tune it. A round-slide CV carb it ISN'T!

Keep us posted.

Hey Mike,

I'm no James Dean or Taffy but, You might want to try a "D" series needle for a WR timed bike. From Taffy's recent posts, probably the DMM (search using DMM). I think the "E" series performs and is easier to jet with the YZ timing.

IF you YZ time, try the jetting in my signature (since you have the needle). I changed to this configuration at the same time I changed the timing and the bike has run pretty dang good since. Of course for YZ timed bikes there is the EMM or EMN needles and the leaner overall jets, that are the latest and greatest.

I have the new jets/needle (EMM) and will let you know what I find between the two set-ups.


Well Here is what I found worked the best.




Fuel Screw 2 turns out


APJ .020

Procircuit T4 with (not so) quiet core

airbox lid removed.

WR timed.

Power rolls on smooth with no hesitation or stumbling however once you open up to about 1/2 throttle or more you get the "RIP YOUR ARMS OUT OF THE SOCKET" acceleration.

Maybe I'll try a DMM Needle to smoot out the power so it's not such a hit.

Thanks for all your suggestions.


can i suggest that you drop the needle a clip position to #3

i would stay with the 45PJ/75MAJ and PS at just 1 turn out and the accelerator pump at just a fraction of squirt. like .5 seconds or less (if anyone can honestly time it!!

i think it'll be better and then i would go to 42PJ with that 75PAJ and the PS can come out 1/2 a turn.

the above info is all good though.


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