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.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Similar Content

    • By Tedstrom
      Alright so I just rebuilt my 2012 kx250f complete rebuild. I put the motor back in the bike get everything hooked up and ready to go it takes a few kicks at first (obviously) but after it starts it sat and idled just fine for a while then it stalled out. Tried to start it again wouldn't start I took the spark plug out of it it looked good I was dark and wet. I cleaned it then put the spark plug back in it it took a few kicks but started right back up again then after a while it stalled out again and now I can't get it to start again!? Any help would be greatly appreciated thank you guys and girls for reading and hopefully for the help!!!
    • By DirtBikeHead
      2015 Kawasaki KX250f - 20 hours
      As close to new as I'd imagine you'd get! I bought the bike brand new, I'm older and have taken extremely good care of this bike. Very little use and is COMPLETELY stock - everything is original. 
      Comes with the title, original book and map couplers for the fuel injection.
      $4700 - cash 
    • By CodyR
      Just thought maybe everyone could post up there youtube channels an we could all help eachother out by subscribing to one another.
      Heres mine ill sub back asap.
    • By bangmyhead
      Time for a top end on my bike, just wondering if there are any alternative Valve springs i can use. I have PC cams and $400 for just the springs and retainers is alil costly at the moment.
      This has been fun in other sections of TT, so I'll start the thread here and see if we can keep it going.
      Let us know what kind of mods, fixes, changes, etc.., you performed today, or just general fun you had with, your KX250F.
      I'll start with.. I installed a correct for my weight Race Tech shock spring, along with a Pivot Works shock spring thrust bearing. Also cleaned out all the nasty yellow plastic/wax crap that passes for grease in the lower shock bearing, and re-lubed it with Bel Ray waterproof.