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Engine surge ?

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I have a 2004 yz250. At idle I've noticed it surging. I've noticed a leak around where pipe meets engine. Could this be the culprit? Hopefully its just a couple of o rings. Please chime in and let me know your thoughts. Yes I did a search for this.

Lucky

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Surge = lean. Means too much air/irradic air supply. Check for leaks, see if turning air screw in 1/2 turn stops it...

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while the bike is idling, spray some WD-40 or starting fluid on and around the intake boot. if it revs higher you have an air leak, causing it to run lean as the others have stated

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When hot or all the time? It could be detonation if it does it ONLY when hot.

Again first check,air leak,lean jetting,dirty carb,carbon build up on the head(seldom),or bad gas.

Or if it's a higher compression motor than stock and your not running race gas.

Even more rare,,,I had a bad cdi do this same thing. Would run super hot,detonate then start surging and at the same time foul plugs. A new cdi finally fixed it.

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