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Kawasaki KFX400 fuel issue?


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Hey y’all I got a kfx 400, rebuilt the carb put bigger inlets on it, adjusted the fuel mixture screw 2.5 turns out and cleaned the fuel petcock. It starts up not so great, it takes full throttle with full choke and cranks for about 10-20 seconds before it fires and while “ideling” it surges very bad and I’ve messed with the idle set and it changes nothing, if you ride it casually it runs fine but as soon as you get on it for more than 4 seconds it stumbles and falls flat on its face and you have to wait for the carb to fill back up with fuel, I’ve checked everything and nothing is blocking fuel, I even put a bigger hose to see if that made a difference. Thanks for reading hopping to hear someone has some advice. 

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  • Ajmboy changed the title to Kawasaki KFX400 fuel issue?


I say “rebuild” I found a cheap carb we had around that had the same part number and took the jet inlets and used them, used some of the gaskets and a few of the screws because when I took of the bowl some of the screws stripped. I have the fuel mixture back off 2.5 turns From the bottom. I have played a bit with it and that seems to be the best running position. I’ve found people have the screw backed off anywhere from 2.5 to 3.5 turns. I’m still using the OEM jets, I was able to clean them out and used air and carb cleaner on them, shook them in a gas and oil mixture (90% gas 10% oil) and then cleaned them off again with carb cleaner, they didn’t seem to be that clogged besides what little trash was in them. 

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Okay so I fixed the rough idle situation, the air fuel screw backed itself off by 2 extra turns, it still does not want to start cold, it takes about 10 seconds of cranking instead of about 20 though but another issue has shown up, there is a catch inside the motor, I think the starter is going bad but it cranks and sounds fine even runs fine. The motor will spin once without issue but as soon as it gets about half way through a second revolution it hits something and you have to keep bumping the starter (about 5-15 bumps of the starter will free it up) and sometimes it’ll catch again about 6 revs later. 

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