yz250f in go-kart

were having a problem at idle .it either is too low or if the idle screw is increased its too much. cant seem to find the sweet spot it had before.the engine only has 15 or 20hr on it.

anybody have any ideas or experience? joel

Not that the 250f is a slouch but.............

Why not a 50HP 426f motor?

That baby would scream!! :)

If you could keep it hooked up!

that would be sweet instead of one of those 125 shifter karts, a 250f shifter kart! :)

i want one!!!

Sounds like your slow speed jetting is off (fuel screw needs tweaking). That or you have an air leak somewhere. Depending on where you are (elevation/temp) I'm guessing that tinkering with the fuel screw would be enough.

Oh yea, and if it was OK before at the same settings and in similar temps then you may just need to clean the carb out real good.

[ July 18, 2002: Message edited by: sirthumpalot ]

Adjust the fuel screw to the smoothest idle, then readjust your idle speeed screw. Did you change the intake system- removed the air box and clamped on a filter?

Give us pictures, we need pictures.

Also, like said above, keep the airbox. You can run with not airbox lid if you want.


Pitch the airbox (sorry Ben) install a clamp on filter. Turn the fuel screw in until the motor stumbles and then (while counting turns) turn the fuel screw out until it stumbles. Then go back to half way between the two stumble settings. Now, while counting turns, turn the fuel screw all the way in. If you less than one full turn, you may want to lean the pilot jet and if your over 2.75 turns out, richen the pilot jet.

Report back what you find. Will this be raced? Does the IKF allow for the 250f in the 125 shifter class? I raced (stock heavy) IKF region 7 about 10 years ago.


wow must be fast


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