03 yz250f hesitating a bit any suggestions?

Anyone else's 03 running a little rough? I rode mine once for 40 miles at the Brown mnt enduro and won't be able to ride it again for around 6 months due to shoulder surgery. It runs great in high rpms but the mid range sounds like it's choking out. I haven't messed with the jetting yet, just wanted to know if it's common.

Thanks guys


Mine does the same thing. I think it's running a bit lean actually. It does it as soon as its a 1/4 turn or so, and the the engine has no load on it. I plan on finding out what the difference is between the 02's and the 03's needle is.

The plan is to bump the main up to a 180, see if it runs stronger wide open, and then mess with the needle/setting.

I found this from an older thread...

Re: Diff between OBELP/Q & OBEKP needles

No. They are basically the same needle with the clips moved a little. It'll work fine. The EKP is half a clip richer so if you were wanting ELP at clip 4 that would be between clip 3 and 4 on the EKP needle. Obviously you can't set it a a half clip location so it's either clip 3 OR clip 4 on the EKP depending on what your bike needs.


'01 WR250F

So the 03's are a 1/2 clip leaner than the 02's, and that agrees with what I was thinking, so it must be right LOL. :)

Any new Info on this?? My buddie is having the same problem, he says at about 4000 rpm, (I'm guessing about mid throttle) I said it sounds like a lean condition and to try raising the needle one position. Thanks for the help! :)

I did put the larger main in (180), and it runs better for it. Not a huge change, just beefier feeling at wide open.

I went 1 clip richer on the needle, and it helped quite a bit, but I think it could still go another clip. It still acts up when it gets hot. Not nearly as much as it did though.

I think I am going to get an 02's needle and see how it affects it, I'm uncomfortable with the idea of having to raise the needle 2 positions. Maybe there's something else different about the needle, or the carb.

My buddie raised his needle and it seems to have helped, but his fuel screw is almost 4 turns out!!! I sugested that raising the clip might just be masking the problem. Some older threads suggest going to a needle with a different taper the FHN available through "sudco"? and actually going down on the main jet. Maybe you can do a search? I think it was originally posted by "Taffy"

4 turns?? Wow, mine is still at factory setting. I never had to mess with it.

Someone posted that they thought the 03 was simply a 1/2 clip leaner than the 02's. This can't be right, cause my 03 would now be a 1/2 clip richer than my 02, and it still bitches when its hot. There has to be more difference to them than what was first thought.

I think I will try the 02's needle first before venturing out into the deeper water of foreign needles though. Mine is almost there, it just needs to be a little fatter at mid throttle. I dont know what to think about your bud's 4 turns though.

"My buddie raised his needle and .....that raising the clip"

Do you know which he did? One richens, one leans..4 turns out on the fuel screw would indicate the need for a richer pilot jet (or leaner air jet).

Sorry! He raised the needle/ lowered the clip one position. Obviously, 4 turns out is not right, got your info on the pilot jet. I'm sure he will get it figured out, just going to take a little time. I'll try and keep you guys up to date, of course this is only one bike, one situation. :D:)

My 03 was doing the same thing. The 03's are actually rich at 1/4 throttle. I experimented with a 38 pilot (40 is stock) and then finally went down to the 35. It is darn near perfect. I will move the clip up one and that should do it. The temp was 55 degrees and 900 ft elevation.

I was thinking a little rich, rather than lean. Spark plug is sooty.....I intend to raise the clip one and see how it goes. Sea level 90 Deg F

Careful with the sooty readings. I believe that comes from the accellerator pump. You gotta read the ceramic to know what the jetting is doing.

How do you correctly read a spark plug? My O3 spits a little in the midrange also. ITFC let me know if your raised clip helps, I am also in Houston. Appreciate any spark plug info. :)DW

I have not had chance to get to the track to try. Hope to this weekend. Want to hook up? From the run up the street it has helped a little. Some finer tuning with a main jet and the pilot needed I think. But until I get to the track I'll wait.

e-mail me dgcrouch@hotmail.com

Thanks guys. I sure hope someone figures out how to fix the problem.

I think I will try changing the clip....

Mine has been running good since breakin. At first, I experienced the same, but now it is fine and still stock. I live in KY. My only problem is when I chop on it at low RMP, it chokes.

My only problem is when I chop on it at low RMP, it chokes

That says you have too big a pilot jet. A lean jet causes it too hang.

Any fixes yet? I'm not going to mess around with my jetting unless it fixes the problem for other folks. Thanks guys.

dave, have you looked at cleaning the carb. You could have some filter oil in the pilot jet's air channel.

Lifting my needle a clip helped a lot. Going one size up (180) on the main also helped.

It never even crossed my mind. I will try it. Thanks.

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