KX 250 motor lock up, what caused this ?

[99kx250Guy]

Hey Guys, Great forum y'all have here! I just traded my ATV for a 1999 kx 250 and the guy showed me all the paper work where he just had the whole entire motor rebuilt, spent over 600$ So today i was riding in 5th gear wot for about 20 seconds and it started bogging down loosing power, then it just completely locked up. I checked the oil and to my findings its Milky looking oil, And then when i tear down the head i find Plastic shaving all over everything. The shaving came from the crank rod assembly. What happened that it tore up?

[okiekx250]

They arent built to run like a car going down the highway. It's a motocross bike. It's meant for quick throttle respose to hit jumps and fly out corners. I've seen many kx250's lock up after being ran like that.

[67_special]

I'll second that. Especially if it's a 2 stroke, shouldn't have happened after 20 seconds though. You really have to ride them hard, if you'd been doing a lot of your ride at a consistent speed or coasting then that would have contributed.


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[j5coach]

You most likely had a lean condition causing the bottom end to over heat, hard to tell without seeing what the piston/cylinder looks like. Another thing could have been a bad crank seal on the stator side. What kind of pre-mix were you using and what where you using for fuel?

[mikel.laundry]

check your reeds. are they still there?

[Beefy2strokes]

Hey guys I can't figure out how to make my own post I have a kx65 with a bad crank and bearings can still get it to kick over but is really hard. And I have to rock it back and fourth to get it past 2nd gear what's the chances of my cases being messed up 2? Some guys trying to tell me my bike is probly toast but I want to rebuild it

[mikel.laundry]

Hey guys I can't figure out how to make my own post I have a kx65 with a bad crank and bearings can still get it to kick over but is really hard. And I have to rock it back and fourth to get it past 2nd gear what's the chances of my cases being messed up 2? Some guys trying to tell me my bike is probly toast but I want to rebuild it

you half to rock most bikes back and forth to get it into second. the transmissions are designed to be moving so it shifts smoother. and do not keep kicking it your causing it more harm. take the top end off. i recomend you getting a service manual from clymer.

[Beefy2strokes]

you half to rock most bikes back and forth to get it into second. the transmissions are designed to be moving so it shifts smoother. and do not keep kicking it your causing it more harm. take the top end off. i recomend you getting a service manual from clymer.

I talked to a shop and the guy sounded confident on getting it fixed gonna cost 600 and wants me to take the motor out and bring it up there is it cheaper to do it myself I don't have a CSS spliter and my crank inside the crank case you can wobble it up and down and the timing screws are striped and I have not tried to kick it any more since I realized somthing ain't right