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Stall on hard throttle

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Hi. So my bike ( kx250f 2009) stall when i give it hard throttle, so when i want to go over something or holeshot, it stalls. I cleaned carb and checked acceleration pump, diaphragm is good, but steel in the middle of diaphragm was rusted a little. So i cleaned it and tested it and it stalls again... So what other can it be ?

 

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A clean carburetor and a good accelerator pump diaphragm, doesn't mean the the carburetor is squirting fuel immediately when you twist the throttle.  The diaphragm could have a small tear in it letting pressure bleed off instead of pushing it further down the line.  The diaphragm could be "bagged out" but not likely.  The tip of the pump nozzle could have a small piece of hard debris caught in the tip of, and soaking it won't necessarily remove it.  Sometimes you have to run a small piece of wire or torch tip cleaner bits in the passageways where fuel flows to dislodge the debris.  It could also be the accelerator pump linkage worn or incorrectly adjusted.  Your leak jet could be too large or missing.

If you pull the carburetor back off, test the pump before you put it back on.  You'll need fuel in the bowl to test it.  As soon as you twist or move the carburetor linkage where the throttle cable hooks up, it should be squirting fuel out of the bore of the carburetor.  If not take a second look inside, and ask more questions before you put it back together.

Edited by WALKINGWOUNDED
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The rust on the metal part of the diaphragm, and the pitting in the diaphragm area, are not a problem.  Although the rust may have damaged the rubber diaphragm, the rusty part is ok.  The carb is easily fixable, you need to know how it works and what to look for.  I can over a few posts help you through it, but we are rooftop deep in water right now.  If you have a local mx shop, he can fix it with it off the bike.  Or maybe another rider that has mechanical understanding of how carbs work.  I'll check in when I can and see how you are fairing.

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Goes lean and quits on throttle .....

- accelerator pump already discussed above. Review those comments in detail.

- Check for air leak in the carb to head boot, such as cracks in the rubber or loose clamps.

- turn the fuel screw out 1/2 turn.

Try that. If still sluggish

- raise the jet needle one clip.

 

 

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