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New to 2 stroke problems... Help!


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I recently bought a 93 yz250 and it ran REAL well. And, like the genius I am, I took everything apart and cleaned it. In doing so, I changed the setting of the air screw and the idle screw. Now it is very easy to start when cold (1 or 2 light kicks) but when it's warmed up, it takes around 10 hard kicks. And when I am in the middle of the throttle, it runs, but not as hard as it should. Low end and top end of the throttle all work well, it's just the middle. I'll post a video if you guys need it. Please help me out!

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Clip position has no effect on starting or idle.

Carefully close the air screw. Count EXACTLY how far out it is. (1.7, 1.55, 1.9, 2.3, whatever) turns. Note this down. You want to be able to return it to this spot, if need be.

Being it is a an AIR screw, the more open it is, the leaner it makes things at idle. Typical setting is between 1.5 and 2.5 turns.

With a cold engine (room temp) you should always need the choke (actually an enricher). Once the engine is heated up, the choke gets closed and the bike is ridden gently untill full heated. Off you go. Therefore, the correct setting of the air screw is with a fully heated engine. It should give you a nice, even idle. Do not try to make the air screw compensate of other areas of the carb that are not adjusted. Do not try to adjust other areas of the carb until AFTER the air screw is properly set.

Once the air screw is set, then you can work on off idle transitions and mid throttle operation, culminating in WOT operation.

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