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1999 KX250 idle adj. screw raises slide, but bike still won't idle. Pilot jet clean.

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Bike runs great.  It just won't idle without adjusting the cable at the throttle.  Slide is down all the way and you can see it raise up when the idle screw is turned in.  But bike will not idle.  Pilot jet is clean as a whistle.  But may be too small.  Would that be causing this problem?  Book shows it should be 52, but it has a 45 in it when I bought it.   The guy I bought it from raced if that makes a difference.  2000 ft., hot and dry. 

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Do you have any suggestions as to why it won't idle?  Or why the RPMs don't change when the idle screw is turned either way?   Thanks.

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Besides the jet, the pilot "circuit" needs to be clean.  Spray brake clean using the little hose through the pilot circuit and all the passages through the bowl and intake areas. Check your reeds for chips and gaps, that will cause it not to idle too.  If all that checks out try a 48 or 50 pilot.  But it should idle with the 45.

Edited by Jeekinz
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Blackwoodz:  The idle screw raises and lowers the slide, but no change in RPMs.  Only way to adjust idle is at the throttle cable at the throttle.  Didn't check reeds.  Any other thoughts before I pull the carb again.  (Pilot jet, main jet and "choke" circuit all cleaned, and cleared.  Float on the money.)  Just throwing this out there, would throttle position sensor electronics have anything to do with this?  

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Besides the jet, the pilot "circuit" needs to be clean.  Spray brake clean using the little hose through the pilot circuit and all the passages through the bowl and intake areas. Check your reeds for chips and gaps, that will cause it not to idle too.  If all that checks out try a 48 or 50 pilot.  But it should idle with the 45.

^^This^^.

If your idle air circuit is clogged, the only way it can get the air it needs to run is by raising the slide more. But a 45 pilot sounds awfully lean, what is your air screw set at, and how does the bike react in the first quarter throttle? 

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The 45 pilot is the stock jet for the 1999 KX 250

The idle screw has 0 effect on rpms?...if so something else is a factor...Even if it will not raise it high enough all the way in to hold a good constant idle..It should atleast change the rpms to some degree.

Edited by Blackwoodz

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OlHillbilly:  air screw set at 1 3/4.  But like Backwoodz says, turning it a full turn either was does nothing.  Response in neutral is rev then bog.  Rev then bog when revving.  Again, blackwoodz is correct, I get NO increase in RPM or decrease in RPM when turning in all the way in or all the way out.  It is like it is doing NOTHING.  Yet, when I look into the carb after pulling the air box boot, it raises it and lowers it as intended.  Weird.  Haven't pulled the reeds yet.  Tomorrow I am off and will pull.

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OlHillbilly:  air screw set at 1 3/4.  But like Backwoodz says, turning it a full turn either was does nothing.  Response in neutral is rev then bog.  Rev then bog when revving.  Again, blackwoodz is correct, I get NO increase in RPM or decrease in RPM when turning in all the way in or all the way out.  It is like it is doing NOTHING.  Yet, when I look into the carb after pulling the air box boot, it raises it and lowers it as intended.  Weird.  Haven't pulled the reeds yet.  Tomorrow I am off and will pull.

And how did the reeds look? 

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Blackwoodz:  The idle screw raises and lowers the slide, but no change in RPMs.  Only way to adjust idle is at the throttle cable at the throttle.  

 

 

That makes no sense. Either way you're raising the slide.

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is it all smokey?

Like, bad crank seal is allowing tranny oil into the mix?

Will rip straight away (but smokey) but wont idle is often a bad crank seal.

48 or 45 or 42 should be fine. Some of them are not right, and will run cruddy...but should idle. Maybe just rough and gurgly. But should idle.

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