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1999 kx250 bogging problem

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Nov 27, 2005
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#1
I just installed a v-force 3 reed cage and now my bike bogs from idle. when u hit the gas from a dead stop the bike will bog until it stalls unless you let the gas off. If you get moving just a little bit though the bog completly disappears. I tried adjusting the air screw but that didn't work what do u think could be the problem?
 
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#3
You need a little more richness off idle. What carb is on the bike? Keihin PWK? I would start by moving up 1-2 steps on the pilot jet.
 
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#5
I think it's lean at idle which is why it is having trouble coming off idle. Fox, you are probably right about the carb having more to it. For some reason I thought it was an older Kawi and those had the PWK. If the carb has an accelerator pump or something, it might not be functioning properly.
 
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#7
Off idle lean is an erratic burst,clogged pilot circuit or too much fuel will bog.That bike has a sensor and a power jet,if it is like a 4t it acts like an ap circuit,it could be the problem.
 
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#8
The original carb on the bike should be a Keihin Power Jet, not the PWK. I know on my PJ (not Power Jet) if I have the choke screw turned in too far, the bike bogs when you come off idle, it's especially bad after long periods off the throttle. Lean or rich, the consensus seems to be the AP circuit. You should check it out.
 
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#9
i had a problem with the ap before it but i fixed it and i have never had the problem until the v-force reeds were put in. its not a major hesitation really but its enough to be annoying. when you ride the bike just cruising around and stuff there is absolutely no miss at all. i turned the air screw out about a half turn and it got rid of it a little bit but it was still there. if it is the ap how can i test it if i can and are they replaceable? if so where could i get 1? thank you for you help i was honestly lost on this problem.
 

DWreck

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#10
patriot, you don't list your location so I have no idea what you elevation is.

I had a 98 KX250 and a buddy of mine had a 99 that I helped get his running right.

You are right about your bike have a Keihin PWK with a power jet. My understanding is very few people mess with changing the power jet so you are basically looking at tuning it like any other carb.

The first thing I would do is double check your installation to make sure you don't have an air leak on the vforce. Vforce claims that you shouldn't need to re-jet if the bike was jetted properly before hand but it is possible you were a little off before. Jeff's 99 was bone stock and was a plug fouler when he got it. We pulled the carb and saw the needle came in the 4th clip. (counting down) We moved it to the second clip and never had another problem.

This was at 900ft elevation, mostly woods, C level rider.

I agree going up one size on the pilot and seeing what effect that has would be a good place to start, you certainly are not going to hurt it by doing this. Good luck, they are a lot more fun when they are running right.
 
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#11
What does the plug say?The power jet sizes are relatively backwards and boils down to a bigger number leans this out.And yes,if you have even a slight leak in the intake it is going to fall off idle.With the engine warmed up,put the choke on and see if it is worse or better,if it is better then you need to richen that circuit.If the engine is running lean with stock jetting,I would suspect a leak.