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Discussion Starter #1
Recently my KX250 has problems idling. When I try to adjust the idle screw it seems to fix it. It will run fine for a moment then all of a sudden the RPM's will jump to about half and the kill switch will not work.
So I bring the idle screw back out to where it was & that will fix the high RPM problem, but then I am back to not being able to keep an idle.

It does have a TPS (Throttle Positioning Sensor) that I unplugged to troubleshoot. It seemed to help a tinny bit. It also has some sort of solenoid. I'm thinking for gas maybe?

What could make this happen? Reeds?

FYI- Running a rich oil/gas mix, 5oz to a gallon.
Recently rebuilt engine & cleaned carb. Idle was fine for a few months.

Any help is greatly appreciated!
 

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Recently my KX250 has problems idling. When I try to adjust the idle screw it seems to fix it. It will run fine for a moment then all of a sudden the RPM's will jump to about half and the kill switch will not work.
So I bring the idle screw back out to where it was & that will fix the high RPM problem, but then I am back to not being able to keep an idle.

It does have a TPS (Throttle Positioning Sensor) that I unplugged to troubleshoot. It seemed to help a tinny bit. It also has some sort of solenoid. I'm thinking for gas maybe?

What could make this happen? Reeds?

FYI- Running a rich oil/gas mix, 5oz to a gallon.
Recently rebuilt engine & cleaned carb. Idle was fine for a few months.

Any help is greatly appreciated!
First tip that I give all the new riders. CHECK THE SIMPLE THINGS FIRST. You are currently doing WAY too much "assuming", and getting too far ahead of yourself. Next, plug the TPS back in, and leave it alone. The TPS has nothing to do with idle. The TPS sends throttle opening data to the CDI for the purpose of altering the ignition timing. Next, Kawasakis KX's always come from the factory jetted conservatively rich. The pilot jet is what is responsible for 50% of your idle quality, as is also 50% your air/fuel adjustment screw. Start by checking the air/fuel screw adjustment (It's the small screw just above the fuel bowl). Turn the screw clockwise until it is closed, then back the screw 1-3/4 turns out. This is simply a ballpark adjustment that should be close. Next I want to comment about your premix oil ratio 5 oz./gal equates to about 28:1 ratio, and you are absolutely unnecesarily gagging that engine with excessive oil. My preference for a premix is 42:1 which is about 3 oz./gal. I encourage using a quality full synthetic oil, and mixed at around 40:1. I'm sure at this point your crankcase is LOADED with raw residual premix oil, and the sparkplug is oil fouled. Try a fresh plug, mix at 42:1, and run the bike for some laps to burn the excessive oil out. Try this first, then post your findings.
Rich
 

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Discussion Starter #4
Thanks Polar,
I've rebuilt a much smaller, simpler 2-stoke. Nothing like this KX engine.
The manual calls for 4oz to a gallon, something like 30:1
I'll try all of the things you mentioned and post the results.
Thanks again Polar!:biggrin:
 
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