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*HELP - KX 250 Idle Surging, Running lean??

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Long story short, I had to remove the cylinder twice last month on my 2003 kx 250 to work on the KIPs, and it was my first time going that far into working on my bike, I believe I did everything correctly, only issue is that after running the bike really hard (wide open hill climbs) the bike slows to an idle then "surges".  Not quite sure how to explain it but each "pop" of the idle is drug out much longer than usual.  It runs fine on the low end but I'm scared to ride it hard because I know from previous experience that running lean can result in a blown engine, another long story.  But anyways, the bikes jetting was done by a mechanic a while ago and it ran perfectly fine in that sense prior to me taking it apart to work on the power valve.  If you need to hear what I'm trying to explain, here's a link to one of my videos I posted where you can see the hills and hear the idle that im talking about. Skip to 1:40 and you can hear it as I sit at the top of the hill. I dont think it is the jetting, so I have researched that air getting into the engine in between the carb and cylinder could be the issue (gasket?) I dont really have any other idea or what gasket or anything, Any help would be great, I dont really want to take the cylinder off again, it could be something completely different than the lean mixture I am suspecting

thanks!

 

 

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8 hours ago, dummy18 said:

Can a dirty carb cause it to run lean

definitely... mine just started doing this too... do you drain the fuel out of the carb regularly?

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I ride it pretty regularly so never drained the fuel, I went ahead and messed with the air screw a bit because I figured I cant screw the engine up too much by making it run richer, better than lean anyways, and the air screw was actually three turns out.  I put it to stock which i believe is 1.5 turns out and adjusted the idle screw to match it, and so far I think the problem is solved or at least better.  I noticed the smoke is bluer compared to the white it was and it seems to idle normal after running hard so i might just go with that

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