Maintenance & Technical > KX250 / KX125

1998 KX250 bogging in at high RPM

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bigspeights:
My 1998kx250 has a problem. at high rpm the power seems to come on and off and if I hold the power on it boggs down a bit and i lose some power. it runs great in the slow tight stuff but crap on the open straights. I have set my float so that it is as high as it can be with out overflowing (I don't know any other way to set it), I have cleaned out my carby, I have cheaked my plug and it is light gray/brown colour, topend is only about 10 rides old, bike starts first or second kick when worm. I have a Bills pipe on it and I am not shure about the jetting but I have never had problems before. Could it be the solenoid on the carby not working and if so how could I test this.

I really want to go riding this weekend and need to fix the bike to beat my buddy's that Ride KTM 450's

hughes:
So this issue came on all at once? Do you have any reason to suspect crank seals? Good fuel supply from tank to carb? Theres a filter screen on top of the fuel petcock inside the tank. Maybe some else can give you more info about the 98 kx250 carb.

KXcam22:
Things to check,

1. Gas cap venting: will restict fuel flow at WOT
2. Jetting: How does your plug look at WOT.
3. Power valve solenoid:  To test this uplug the electrical connector to disable this.  It there is no change in how it runs then it is NOT this.

Set your float level back to the stock level.

Give these a check and post back. Cam.

azdirtrider75:
I had a similar problem a few months ago with my 2002 KX250. It turned out that my gas cap vent hose was kinked and caused a vacuum, reducing the fuel flow to the carb. At slow speeds it ran fine, but at mid to WOT it would bog.

Good luck

bigspeights:
Thanx for your help so far. There is heaps of fuel coming from the tank to the carb. how do I set the float to factory setting. The problem started on my last ride. Just before the ride I had changed my float level because fuel was coming out the over flow. I think I have changed the float back now but I don't know how to set the float properly. does the soionied in the carby come on at high rpm to reduce the fuel flow. if so if this was not working would that mean that if I unpluged it and the bike ran the same this would be the problem. could it be that my bike is getting to much fuel at high rpm. also is there an easy was to make the seal where the pipe goes into the head better, some oil splatters out of mine.

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