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08 kx250f blown up.

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Hey guys. I just picked up an 08 kx250f on a trade for a plow I had lying around. Anyways, the bike doesn't turn over. It was blown up at a race. There's no holes in the block so it shouldn't be too too bad. I'm just wondering, what should I do/check first before I tear it down completely. Thanks.

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..first get a service manual..i purchased an 07 to restore and found an 06 service manual online.. you should inspect the oil. check for shavings. from there, with the proper tools start tearing it open..open the head and check the clearance and timing, remove the cams and inspect the journals they sit on and the buckets for any discoloration or marks usually due to an  overheating bike...

You mentioned it does not turn over...is this by the kick starter? if so try spinning the crank on the flywheel side going counterclockwise...Also try to get the bike in neutral on a stand and see if you can rotate the rear tire back and forth easily this should single out any possible transmission problems...you can also try shifting just to make sure the shift drum and or forks are not worn, bent, or seized (it helps with the right side clutch cover off so you can see the shifter mechanism work) 

 

from there just try to pin point where it locked up...

 

Valve seizure
Valve lifter seizure
Cylinder, piston seizure
Crankshaft seizure
Connecting rod small end, big end seizure
Transmission gear or bearing seizure
Camshaft seizure
Kick shaft return spring broken
Kick ratchet gear not engaging

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Funny story.  I bought a bike that was seized once for $1,000.  Kick start did not move.  Upon getting it home and ready to tear into it, I noticed the clutch cover was dented.  Must have fallen on a rock.  It was locking the clutch basket.  New clutch cover, perfectly running bike.  Wish I could buy more.

 

Racer is right, of course.  First step is a full shop manual.  Worth every penny . . . esp if you find a PDF version that is legal.  Next step is to find the problem.  Should be fun, and maybe you will find it's a simple fix.  Let us know, please.

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Ok so I got around to looking at the bike some more. There is no oil. The previous owner drained it. One thing I noticed was where the cylinder meets the bottom end, I can see shards of the gasket sticking out. Not like far out but I can see the shredded ends of it sticking out a little bit. Oh and I just noticed there's a typo in my post. The bike is a 2009 not 8

Edited by jaradzoida

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Where in NY are you from? Im currently working on an 07 that i picked up for cheap..it too was not running but it was turning over.

 

Before doing anything i removed every orifice..drain plug, timing plugs, and rad cap and would kick the bike..i noticed air would come out of the rad cap and some out of the oil drain plug..i compared it to my 10 and realized that the head gasket was bad and the bike needed new rings..when i drained the oil i saw the coolant had sank to the bottom of the case..

 

I then split the cases to replace a cracked stator side crankcase, installed new bearings, removed the valves and cleaned the seats, the carb, boot, filters..now the bike starts first kick  :ride:

 

You mentioned it does not turn over, can you turn the engine over by using a socket and turning the crank from the stator side?what do you mean about the gasket sticking out..like it overlaps? im sure it is not the cause, but replacing gaskets while you do an overhaul is highly recommended. 

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man so far everyone that has posted are from NY... go team NY

also I would pull the spark plug and look down there and see what you can see then tear the head off.... it doesn't take long to take things apart

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man so far everyone that has posted are from NY... go team NY

also I would pull the spark plug and look down there and see what you can see then tear the head off.... it doesn't take long to take things apart

 

Things are not looking good for NY then.............

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Ok so there WAS oil but it wasn't enough to show up in the sight glass. Nothing unusual in the oil. So, I have a pretty good understanding what happened. The prev. owner ran the bike with 1/4 of a qt of oil in it, ran it hard and wheelied it, so the oil went to the back of the case, the owner said it overheated then died. He said he started it up again and it started but it was knocking. That's the story behind this. I'm almost finished taking the motor out of the bike. I got a few more bolts and then it's out. I'll post here when I tear the whole motor down.

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Intake valve bucket failure from lack of lubrication.  That seized the valve down into the piston.  Does the crank still turn OK?  Loss of oil usually scores the rod pin in the crank causing it to seize.  Also possible that the valve to piston impact bent the rod.  The head needs a tear down and inspection it might be salvageable with a valve job and new valve bucket.  The piston looks damaged and should be replaced.  Just really check the crank and rod well.  Loss of oil is a bad thing with the crank.  Main bearings and transmission should be fine. 

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Hey guys. I just picked up an 08 kx250f on a trade for a plow I had lying around. Anyways, the bike doesn't turn over. It was blown up at a race. There's no holes in the block so it shouldn't be too too bad. I'm just wondering, what should I do/check first before I tear it down completely. Thanks.

 

I just picked up an 11 sort of same story, except this thing shattered a piston.

There was 1/4 of a piston still attached to the rod when it came apart. just enough to really hammer the cylinder and make sure the rod got &%$#@!ed in the process.

 

Parts list so far::

 

cylinder - see above

piston - see above

rod - bent

intake valves - bent

intake guides - cracked

 

I think I'd prefer a rebuilding a fully exploded motor over no oil. Although on the surface, it seems like the motor I got suffered more damage than the melt down you got.

I expected everything I got and figured that into what I paid for the bike, but I got caught off guard by the cracked valve guides. The guides themselves are cheap and easy enough to replace. But now I have to have the seats refinished, and that will add to the overall cost.

 

I'll end up with an 11 with a much fresher motor than I was planning when I'm done. So far I'm into it for a little over 2300.

And that doesn't include the valve seat work it's going to need. So I'll be closer to $2500 when I'm done.

Hopefully its worth around $3k.

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