05 yz250 idle inconsistent, dies.

I'm having an issue with the idle on my yz. It is real inconsistent, high then low. Sometimes when I come into a corner pull in the clutch and the idle drops all the way to nothing and it dies. I have cleaned the piss out of the carb, made sure all the vent hoses are not plugged.

The reeds are not cracked or chipped. Jetting is good, and it runs great above idle. Any ideas??

might be the coil?

Please elaborate on the coil? How would this only effect the idle, is there a way to test it. Or do you just replace it and see if that fixes it.

In the manual you'll find the OHM values to test the specs.

Primary Coil resistance is 0.20 - 0.30

Secondary Coil resistance is 9.5 - 14.3K


That's from the 09 manual, 05 should be the same.

Sounds like a classic air leak to me.

Sounds like a classic air leak to me.


Yup was leaking air at the reed block/boot junction. Fixed that and the idle is smooth and consistent and it will idle down to nothing and still keep running. Now the problem is that the idle screw(plastic) must be worn on the end that contacts the bottom of the slide. Even screwed all the way in till the spring gets coil bound the idle is too low. If I remove the spring then I can get it to reach a proper idle speed. Has anyone ever see these wear out??

You fixed the air leak now you must fix the jetting. I would venture to guess your jetting was compensating for your air leak.

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