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04 wr250f jetting with Bills pipe slip on woes

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Put on a bills pipe thunder series slip on and now there is a quarter to mid throttle hesitation like a 2 stroke clearing and won't run hard at full throttle and feels as if the rev limiter kicks in early. It is really anoying as the bike ran well with the standard pipe. Should I richen the needle and main because it can breathe better or go leaner ??. I have also opened up the airbox using the cutouts. The bike is running standard as delivered jetting for the aussie market. I do know it is running a 170 main.

All help really appreciated. Cheers.

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I'm running a 180 main at about 500'asl with the stock pipe and air box cut open, so yeah, you may be lean at a 170 main, especially with a free-breathing pipe. Jump to the 180 as a baseline, and creep upwards from there.

If it's hesitating at 1/4 to mid, then that problem may be in the transition from pilot to needle. I'd try dropping the clip one position then adjust the hesitation out with the pilot screw. If you can't completetly clear it, then drop the clip one more. Since it is in the transition zone, you might end having to buy a different needle. Might be a good excuse to buy a JD kit.

Just my $.02

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Thanks Barton for the info. Just to get a bit more specific as the aussie jetting standard may be different to the USA model, the main is #170 as said, the pilot is #40 the needle OBEKQ-4 and the clip on the 4th position and the pilot screw 1.5 turns out. I was able to get this info out of the manual. If any of this seems way off please let me Know. Looks like the main is way off if your using a #180. What clip position do you use ?

Any other WR250f owners out there ? What specs are you using ? Cheers from downunder

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Since I use the JD kit, our clip positions won't compare. I use JD's blue needle at clip position 3 in the summer and at position 4 in the winter.

Our pilot jets are slightly different. My WR wouldn't run well if I was cruising at 1/8-1/4 throttle, so I went to a 42 pilot and that cured it. I don't think it's a necessary change though if yours is not missing at low throttle settings.

Re-reading my post, and considering your stock needle, it might be better to start at 178 if you decide to increase your main jet.

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