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89 kx250 low idle

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The idle screw on the the carb is screwed all the way up to the lock nut between the head of the screw and the carb body. The bike idles but it's very low. When i remove the locknut, i can screw it in a little bit more and set the idle to where i like, but after running it for a little bit, the screw backs its self out. Any help is appreciated.

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That clip is the needle set on, and how many screws turned out is the air and fuel screw

The clip is set to the second from the top, and the mixture screw is just about 2 turns out from seated

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What condition is the engine in?  Having to turn the idle up can be an indication of top end wear.

The engine appears to be in good shape. There is plenty of compression, it starts on the first kick, and has plenty of power. When I looked through the exhaust port, the piston and cylinder looked good too.

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46 minutes ago, The Stone said:


The clip is set to the second from the top, and the mixture screw is just about 2 turns out from seated

Some history would be kind of nice.  Such as did this idle problem just develope,  and have you tried to do anything other than the idle screw,  how was the low speed jet setting determined?   If you take the carburetor off and look down the throat while you are working the throttle what do you see?  When it comes to rest how much of an aperture does the slide have?

Edited by ossagp

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Some history would be kind of nice.  Such as did this idle problem just develope,  and have you tried to do anything other than the idle screw,  how was the low speed jet setting determined?   If you take the carburetor off and look down the throat while you are working the throttle what do you see?  When it comes to rest how much of an aperture does the slide have?

I picked the bike up last thursday and got no history with it. The idle problem has existed since i've had the bike. On sunday while in the woods, i turned the air screw out to bump up the idle a little bit to make it manageable. I see the slide moving up and down freely and coming to a rest on the idle screw. The aperture is somewhere around an 1/8 inch.

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with that much opening you should be idling high enough to hear the angels singing.  plug is coming out black and wet etc? 

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1/8" on the upstream side would be accounting for the slide cutout I imagine.  Probably less than 1mm on the backside.

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yeah could be,   guess I should have said "candle it and see how much light  you have".  

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Have you tried cleaning the carb? It might not help, but it's something to eliminate from the equation.

 

 

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Have you tried cleaning the carb? It might not help, but it's something to eliminate from the equation.
 
 

I've cleaned the carb twice and am pretty confident I got all the little passages. I also looked at the reeds and saw some light coming through, flipping them made it worse. I then saw that the edge of one of them was chipped so they've gotta be replaced.

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