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I am having an issue on a 2002 KDX 200 I am working on for a friend.  Bike starts and runs great until I start moving the fuel around in the float bowl.  I can do this by pumping the forks, lifting the rear wheel, or rolling and braking hard.  When I do anyone of these things the bike floods and dies.  I can keep it going with more throttle but it is so fat and burbly.... like the choke is on.  I am certain that float level is affecting it but my issue is very strange:

I adjusted float height to spec (16mm) and even went as far as taking the float out of my bike that is running great to see if that would fix it.   It did not.  Here is the strange part.  If I lower the fuel level in the float bowl, by adjusting the float way out of spec, the bike runs better.. except under hard braking.  If I turn the fuel off at the petcock the bike will run like crap.... then run pretty good.... then run perfect until it runs out of gas...

It seems like the fuel is getting pulled up through a jet or through the choke.....  It is definitely flooding out.  I replaced the choke plunger in hopes that would fix it but no...... I have installed my needle valve to see if that was the problem... nope....  I have had the carb apart 4000 times and I cant see anything wrong.

What could cause this??  Is something plugged and causing the fuel to get pulled in the wrong port?  Is something broken internally on the carb body?  I am at a total loss and this guy wants his bike back....  HELP!!

With all respect... before anyone suggests it... This is not an electrical issue, or a clutch issue, or an idle adjustment.  I have proven to myself the fuel is sloshing in the bowl and flooding the bike.... I just do not know how to fix it....  Surely I am not the only guy to run into this.

Thanks in advance for any expert advice you can give.

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Check the floats, ensure they are not leaking. Remove and shake, listen for fluid, if you hear some, buy new floats.

Also check the float needle valve seat and needle, ensure they are clean, undamaged and no corrosion.

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Speaking of KDX 200's,  I had one that acted somewhat like that,  but no matter how much playing I did (I am considered by some to be float phobic) I did with the float it still did that,  and often flood if left for long times with the tank valve on.   It would go through periods where it would run high and blow lots of smoke,  and others it would not.  It would flood out going down hills SOME of the time.   Some of the time it actually leaked on the floor.   

A friend of mine sat in my driveway and held the float up with a screw driver,  etc while she rocked the bike around or just sat next to it,   she found out that the needle seat was leaking behind the seat itself and running down the backside of the float needle tube SOME of the time.  She fixed it with epoxy and we used it the rest of the summer.   (Said friend is entering her senior year in an engineering program this fall.)  

But part of what that PWK equipped carburetor was doing as your subject is.  I wouldn't have been trouble shooting it the way my friend did,  but her way worked for that bike.  

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Thanks for the responses.  I have used the float and the float needle from my perfectly running KDX so I feel like I can eliminate those components....  I am intrigued by the second response.  

so it was running down the brass barrel that the needle seats into?  Interesting and that would explain why nothing is working to fix it.  Is that part replaceable?

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Yep,  that is where we found it.   The confounding thing was that it was not always acting in the same way.  As if it was loose enough that that it sometimes shifted.  When the carburetor did not pass the "air test" I let my young friend go looking for why and she finally ended up putting water in the tank and doing variations of ways to hold and move the float to see how it shutoff.  So short of buying another carburetor the epoxy was her way of fixing it.   As near as I know the part is not replaceable in that I have yet to see one listed in a parts manual.   Maybe I am just not looking in the right place,   as I never tried SUDCO etc to get one.  I never have pulled an old one out either.   Probably the only thing I like better about the Mikuni carburetors that I have dealt with.  

16 hours ago, heatmaker said:

Thanks for the responses.  I have used the float and the float needle from my perfectly running KDX so I feel like I can eliminate those components....  I am intrigued by the second response.  

so it was running down the brass barrel that the needle seats into?  Interesting and that would explain why nothing is working to fix it.  Is that part replaceable?

 

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