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04 yz250f idle issue

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Bike gets hard to start after its warmed up and will not idle for more than 5 seconds. When cold it will start 1st or 2nd kick. Could this be a blocked fuel screw passage? Already checked cam timing and just reshimed the valves.

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Service the entire carb

 

http://www.dirtrider.com/features/protips/141_0707_keihin_fcr_carb_rebuild/

 

Most likely you have some corrosion inside the carb

 

The fuel screw passage is huge, and does not block eaisly, unless you have a rotting body gasket.

 

Hard starting when warm typically means a rich condition, like a corroded pilot jet.

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Service the entire carb

http://www.dirtrider.com/features/protips/141_0707_keihin_fcr_carb_rebuild/

Most likely you have some corrosion inside the carb

The fuel screw passage is huge, and does not block eaisly, unless you have a rotting body gasket.

Hard starting when warm typically means a rich condition, like a corroded pilot jet.

None of the jets were corroded. I've already been inside the carb and it didn't seem to be gummed up. And the plug reads that the bike is running lean. It's got 42 pilot jet and a 153/158 main. Can't really see the number that well but the hole in the jet is spotless

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Stock and aftermarket pipe jetting specs:

 

YZ250F 180 42 OBEKR 4th 1.625 turns           Pro Circuit 182 45 OBEKR 4th 1.75   turns

 

 

Idle issues are pilot jet circuit related

 

Re adjust your fuel screw, making sure to reach highest possible idle USING THE FUEL SCREW, then re adjust idle if too high, with the idle screw

 

Check fuel screw oring for damage

 

Ideally you would want an R&D fuel screw to make this easy, and to check it often

 

If you have more than 150 hours on the carb, replace slide seal and the needle jet (not the jet needle) as they are wear components

 

You can't read a plug using pump gas, too many additives. Grey-brown is typical with pump gas.

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Stock and aftermarket pipe jetting specs:

YZ250F 180 42 OBEKR 4th 1.625 turns Pro Circuit 182 45 OBEKR 4th 1.75 turns

Idle issues are pilot jet circuit related

Re adjust your fuel screw, making sure to reach highest possible idle USING THE FUEL SCREW, then re adjust idle if too high, with the idle screw

Check fuel screw oring for damage

Ideally you would want an R&D fuel screw to make this easy, and to check it often

If you have more than 150 hours on the carb, replace slide seal and the needle jet (not the jet needle) as they are wear components

You can't read a plug using pump gas, too many additives. Grey-brown is typical with pump gas.

That's running on vp race fuel.

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That's running on vp race fuel.

 

 

Oxygenated C12/C16 ??

 

That fuel requires re-jetting because of all the extra oxygen in the fuel.

 

Call VP and ask what they reccomend, but I would go up on the main jet one size for sure, and verify you fuel screw setting vs. pilot size

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Oxygenated C12/C16 ??

That fuel requires re-jetting because of all the extra oxygen in the fuel.

Call VP and ask what they reccomend, but I would go up on the main jet one size for sure, and verify you fuel screw setting vs. pilot size

C12. And yes. I ordered a 160 main and going to go to a 45 pilot. I ordered oem rebuild kit to go in it as well.

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