Carb Needle Profile Comparison YZ vs. WR


Did he look at needle options for the '01YZ250F?

The parts fiche on-line shows OBELN is part number 5NL-14916-EN. It is listed as an option for the YZ250F.

Brett, got it on the other thread.


[This message has been edited by James Dean (edited September 06, 2001).]

Finally got my carb parts ordered. it only took an hour to do it! :)

Just in case anyone wants these part numbers, (for sea-level jetting, per the master, James Dean) here they are:

Main Jet #168- 4MX-14943-91-00

Pilot Jet #48- 4MX-14948-06-00

Pilot Air Jet #100- 7A9-14943-27-00

EBLN Needle- 5NL-14916-EN-00

I will post results asap. Should receive these within a week or so. Thanks again JD!


One word says it all! James Dean, you are the MAN!

Installed the carb parts above, and the bike really has more OOMPHH! The mid range is waaay better, and the top end seems better as well. I didnt get to do much hi-speed cruising, (flip-flops, no gear on), but it was building power much nicer, and acceleration was vastly improved. I only noticed a little sputter from 1/8 to about 1/4 throttle. Im hoping this can be cleared up by playing w/ the PAJ? Any suggestions from the pros would be much appreciated. Thanks again JD!



Glad to here you are having such great luck with the jetting, BUT YOU ARE KILLING ME !!!!! I'm still waiting for my jets to come in so I can join the fun. -- MORE POWER :)



Glad to hear you're having fun with the increased mid-range power. :)

Needle profile graphs can be seen at:


Hey James Dean,

I would like to pick your brain for some jetting tips for my bike. I ride a 2000 WR400 that has the airbox lid removed, an e-series pipe with seven discs. It's a canadian model so it doesn't have the throttle stop and it is still WR timed. I ride anywhere from 0'-6000' feet elevation. I've tried the archives and was beginning to go crosseyed with all the info. Any help is greatly appreciated.


Read my postin on Aug. 29 of this thread (above). Same recommendation is for your bike also.

Thanks Jim!


'01 WR426 here. Will be doing the exhaust soon. 2 questions:

1. Should I wait until I do the pipe to do the above jetting & needle change? (uncorked US stock pipe now)

2. Does the BK mod effect these recommended settings? (BTW, I haven't done the BK mod.)

Suggest you just do it as described and not wait for anything, exhaust or YZ timing. The BK carb mod (reduces accel pump flow) will probably work better with 1 clip position richer on the needle, #5.

Happiness is....putting in the exact parts and settings recommended by James Dean followed by a short ride to verify that improvements have definitely been made. For me, this is a rare thing with carb rejetting.

I now have:


#48 pilot

#100 pilot air

1 turn out

#168 main jet

BK mod, around 0.5 sec squirt

no airbox lid

grey wire cut

WR timing

and it feels very good everywhere in the throttle during my initial short road test around the neighborhood. More testing to follow tomorrow after work in the dirt.

Thanks to everyone that has spent countless hours tinkering and thanks to the providers of sage advice, such as James Dean, for making this re-jetting adventure something other than the nightmare I'm accustomed to.

Preliminary report: The front wheel comes up easier than ever before in 2nd gear and the power stays with me after the accelerator pump discharge stops....whereas it used to require more throttle to loft the wheel and I think I NOW understand what some discussion threads have said about the power falling off due to the lean condition that would occur when the accelerator pump squirt ended.

More information to follow after I have a chance to ride it properly in the dirt this week.

Jerry in Deltona, FL

Great to hear this, Have Fun!

Thanks again JD. Like jerry, Im having great results with the jetting changes. Had to lean my needle a clip, but right now shes really humming well.

My question is this, (to all), What do I stand to gain by doing the BK, ACV, and YZ timing? Can I expect my WR to feel like a WZ? Would I then be squeezing every last breathe of power out of it? Will it feel snappier?

When you are able to snatch this needle retaining clip from my will be ready Grasshopper.


I also heard that the best of all these mods is the "FU" mod. Ever hear of this one??


FU? FU? "Fill'er Up"???

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