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YZ 250 idle issue

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Not a newby, have been riding 2 and 4 stroke dirt bikes for 45 years, so here goes.

 

Just purchased a 98 YZ 250 for the grandson, did the top end, fixed the leaky water pump, clean the carb, set it to stock jetting. Air screw 1.5 turns out.

 

Sitting on the stand in the garage it idles fine and I can adjust with the knob on top of the choke. Kid goes and rides for 20 minutes and it won't idle and the knob makes no difference. WTF

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I would vote for the plugged idle jet too.  Might make sure there is no fuel line restriction and the tank cap vents well

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It's normal for idle speed to change as the motor warms. I think all you need to do is set the air screw for max idle when the motor is warm. You probably already know this stuff, but good old Canadian Dave's tips may be helpful...

http://dirtrider.net/forums3/threads/carb-tuning-canadian-daves-kdx.184671/

It's cold (lean) when it starts. Richens up as the engine gets warm.

Don't do max idle. Max idle IS lean. It really hampers low rpm power. A clean or even slightly rolling idle is better.

Edited by seer

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