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Weather changed, my jetting went to crap?

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My YZ250 runs nothing like it used to. It's about 75 degrees out there and it's gotten real difficult to ride. Before, when it was about 20 degrees cooler it ran great.

The bike has trouble starting hot and the biggest issue I've got is the throttle response. The bike jerks real hard when I get on the gas [lightly, when I'm trying to finesse the throttle} and I end up doing the on/off/on/off/on/off dance while I'm trying to ride. This happens at any rpm, but it only happens up up to about 10% throttle. After that, it does fine and gets into it's stride. You can whack it wide open and it f$#ks right off.

Please help. Last two rides have been absolute shit. The bike is wearing me out trying to control it and I'm not having any fun at all.

I have no information on how it's set up, but it was great before the weather came around.

TIA.

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For baseline info it would be nice to know what jets you have in the carb right now. I am sure we can help if you find out.

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My YZ250 runs nothing like it used to. It's about 75 degrees out there and it's gotten real difficult to ride. Before, when it was about 20 degrees cooler it ran great.

The bike has trouble starting hot and the biggest issue I've got is the throttle response. The bike jerks real hard when I get on the gas [lightly, when I'm trying to finesse the throttle} and I end up doing the on/off/on/off/on/off dance while I'm trying to ride. This happens at any rpm, but it only happens up up to about 10% throttle. After that, it does fine and gets into it's stride. You can whack it wide open and it f$#ks right off.

Please help. Last two rides have been absolute shit. The bike is wearing me out trying to control it and I'm not having any fun at all.

I have no information on how it's set up, but it was great before the weather came around.

TIA.

According to my hand dandy JD jetting guide, you s/b running about 2.5% richer now. One size down on pilot and/or needle clip will probably put you a little leaner than you were when it was 20 deg colder. One down on the main will probably be close to where you were, but you mentioned only noticing a problem @ 10% throttle. Simple solution... turn air screw out! I would try a 1/4 turn at a time and test. If you end up more than 2.5 turns out, you need a smaller pilot jet, and then start over tuning air screw. Hope that helps...

Regards,

Colin

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