2013 kx250f newly rebuilt wont idle, runs fine.

I just rebuilt a 2013 kx250f for a friend. I put all new Moose valves and springs with a new Wiseco piston and gasket kit. I had a professional mechanic cut the valve seats and I put everything together very carefully.


The bike runs fine but it wont idle. I started it up with the choke and it ran like normal but when I turned the choke off the bike's idle dropped down and died. I was able to start the bike without the choke if I gave it a little throttle.


I turned the idle way up, if I gave it a little gas it would idle for a couple seconds as if the throttle was hanging and then it would die.


I checked all the electrical and reconnected the wires. I may have overlooked something?


Any help would be greatly appreciated!



Does anybody have any ideas?


We had a similar issue with a 14. Fully rebuilt top to bottom.

it would not kick start at its first start. After it ran for the first time it would then kick start.

I checked and rechecked all the usual stuff.

one thing I forgot about. These bikes have some sort of a relay under the tank that shuts them down when they crash.


we never figured it out before the owner took it back. 

I was thinking some dirt or debris might have fallen into the fuel line and made its way to the injector.

It arrived at my shop disassembled with the fuel line completely open.

Ever find the solution?

I would recheck you valve clearance. That's the first thing I do when ever a 4 stroke MX bike is acting weird.

I have the same problem, redid the valves last week, took it to the track this weekend and had the same problem again.

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