03 WR 250 jetting/mods

Anyone jet their 03 wr 250 yet? I see there is a big differance in the mj from the US to non-US bikes? 185 vs 172mj? I tried yz timming my wr with negative results. :)

yamafreek_hawaii, how is that thing working for you? I still have 2 torture filled weeks to go until I throw my leg over one. I am dying for some more ride and tell.


Just put my 01 FMF Q on my 03 WR and went to a #38 pilot. It cleaned up the bottom but still has a hesitation at 0-1/4 throttle.Blocked off the air cut valve with no luck. Next I will try a #80 and #100 leak jet (#90 stock) Not sure why the big main jet gap between US and all others. Also different needle's (OBELP all others and OBDVS US) How is yours off idle? Any bog? Have you rode it with the gray wire cut? Any one else have one?


I still have a hesitation in the same range as you with no luck getting rid of it.


What have you tried to fix the hesitation? My pipe made it worse and the #38 pilot made it better. To me that does not make sense. Try the #38 and let me know.


I am slacking! I have to admit I was hoping that it would go away after break in (yea right) I am a little flusterd. I think I will wait a bit to see what others do, that actually works! hope we find it soon.

sounds like you 03' WR guys have the same 1/8-1/4 throttle "miss" as the 03'YZF has...so far there's no known fix other than a vortex ignition, which leads me to believe it's something with the TPS settings on the 03's.


That has not been as big of a prob. as the off idle, out of slow corner bog I have. I was pulling it into my garage after riding in the street (trying to look really cool) and I came to a slow creap, hit the gas and dang near went over the handlebars. really cool hu.

Sounds like a lean condition and/or and accelerator pump calibration to me. Putting a higher flowing pipe and opening up the air box on will exaggerate the problem. I would mess with the needle position and leak jet. Go richer on the leak jet until it runs worse and then go back two. Please no flame mail on this one but I think a Powernow would fix a lot of your issues with this problem. I have jetted tons of motorcycles (street and dirt) with modifications and off idle hesitations is almost always a lean condition (or ignition timing) when you try to make things flow better and increase performance on a bike that is already lean from the factory (which most are). I would note the ignition posts also as it seems to be a wide spread issue with the 03 F's.


I do not think that the power now will work without jerry rigging on the 03 but I will try that. As for all the jetting, and messing with the carb, that is very new to me so I want to reserch it all out and understand the carb before I mess. Thanks for the info.


I read the post about the YZ 1/8-1/4 miss. This does not seem to be a problem with my and from what I have heard others 03 WR's. If this is true maybe the YZ guys should look at the jetting spec's and ignition part #s to see what is the diff. between the 03WR's and 03YZ"s.


I fully agree with you on the lean condition but why did it run better (less 0-1/4 miss) with a leaner pilot jet after I put the FMF Q on ? It also seemed to miss more once it warmed up. This would indicate a rich cond (at 0-1/4 only)I raised and lowered the needle with stock #4 position best. I will try a # 80 leak jet and see where that goes or should I try a #70. (stock #90).On a side note why do you think there is such a big gap in main jets between non-US and US bikes (#172 non-US #185 US) Non-US bikes do not have the air box snorkel.


Does power now list a unit for a 03? will a 01-02 fit? Looks like it should. let me know if you try it.

Yz guys


The jetting on my WR without the 1/8-1/4 miss is as follows:

Main #185 and 172 non-US

Pilot #40

Needle OBDVS and OBELP non-US # 4 position

Leak Jet #90

Float height 8.0 mm

Manual did not say pilot air jet or starter jet size.

Any one have the part # to the WR and YZ CDI unit? If the vortex helps and they are different that may be the problem.

c&b/Bobixr250 - http://www.worldpowerracing.com, the maker of the PowerNow gizmo does list 03 versions for the 250F, the 02 250F PowerNow gizmo won't fit on the 03 bikes - the 03 intake air bell is now one unit. The older intake air bell can be taken apart into two pieces and the PowerNow gizmo replaces the end piece - see pics in my sig. Look at your 03 carb's intake air bell and compare it to mine - you'll see what I mean...


thanks for that info.


what is your factory setting for the pilot screw at? I messed with mine and it did not make a diff. on 0-1/4 bog

1 7/8 turn on fuel screw. I tried all settings but no change at all. Try the #38 pilot jet.


I will see if I have time tomorrow to try that.

will your bike stall if you open the trottle wide from idle? mine does everytime (seems to be getting worse)

yes, only if i open her up fast riding or any time on the stand. Smooth role ons are ok.


Is that normal?

No I had to play around with my 01 to get rid of it also.

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