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Engine Seized - 13 KX250F

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I didn't even make 1 lap today and the back tire locked up, bike died, and I couldn't kick it over afterwards. After getting it home, I tipped it on its side and pulled the stator cover to find a bunch of copper/aluminum shavings in the filter screen, engine casing, etc. I assume it's the lower connecting rod bearing but don't know for sure yet.

 

Could the shavings or engine seizing have damaged the crank? How can I know whether it's still good and just needs new bearings versus replacing the crank? Is it the crank or crank bearings which cause something like this to happen? The previous owner changed air filter every other ride along with oil.

 

The previous owner also indicated the entire top end had just been rebuilt prior to selling, is it at risk of being damaged too or would the shavings have all stayed in the bottom end? Just wondering if I need to tear it all down too and investigate.

 

 

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I would be very reluctant buy any vehicle (car, bike, whatever) that the owner claimed recent engine work.

Prior to selling the bike there was likely some type of engine failure and it was put together as cheaply as possible with the intent to sell.

 

Edited by allrightythen
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A 2013 MX bike if it has been raced is way overdue for a complete engine overhaul including crank, all bearings and seals.  Unless you got a killer deal on that bike you bought a worn out race bike.  Never, ever go by the word of the previous owner without hard proof that any work was done correctly with quality parts, or him saying it is just smoke.  Why do you think Hotrods does such a booming business on cranks for MX bikes and companies like Wiseco sell zillions of pistons?  MX bikes need rebuilds fairly often, including the crank.

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Don't order anything until you've fully disassembled and closely inspected everything for wear and damage. (including the cases)

 

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Things to look for:
cracks
prior repairs (welds, JB weld)
stripped/cross threaded/worn threads
bearing race area condition (dings, scores wear from prior repairs, loose bearing fit)
gasket / sealant machined surface condition

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Any recommendations on good tools I'll need to split the crankcase, pull the crank, bearings, and anything else I might need to tear the engine down? I'd prefer to buy tools which I can reuse on future bikes if possible.

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Any recommendations on good tools I'll need to split the crankcase, pull the crank, bearings, and anything else I might need to tear the engine down? I'd prefer to buy tools which I can reuse on future bikes if possible.

Your going to need a fly wheel puller, case splitter, crank puller, clutch basket holder and possibly a high/low socket. I've seen cranks go out on new top ends destroying the piston and cylinder.

Tusk makes good splitting tools and motion pro

Go OEM on the bearings

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Second that with OEM on most parts.  But, even though some people give aftermarket engine parts bad reviews, I oftentimes think it is the mechanical skills of the reviewers.  We have 2 CRF450Rs with HotRods cranks and Wiseco pistons that now have a bunch of hours since rebuild and running just fine,and ridden hard.  Same for the big bore XR250R with a 277cc Wiseco piston.

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Your going to need a fly wheel puller, case splitter, crank puller, clutch basket holder and possibly a high/low socket. I've seen cranks go out on new top ends destroying the piston and cylinder.
Tusk makes good splitting tools and motion pro
Go OEM on the bearings


I've ordered all the tools you mention but the high/low socket. I'm not seeing that. Are you just saying deep well socks?

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I've ordered all the tools you mention but the high/low socket. I'm not seeing that. Are you just saying deep well socks?

It's a possibility you might need one to get the clutch basket off of it has that but. Not 100% sure you do. If you serviced your clutch and it's a standard nut then disregard the high/low socket. IMG_1948.jpg

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I've got the top end torn down but got stuck on the clutch hub nut. The tusk clutch holder is too thick to fit in the grooves and slips when I try to use a ratchet and socket.

I'll try my impact tomorrow and hope that provides better results but I'm not sure how I'm going to torque it back down during assembly. :(

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I've got the top end torn down but got stuck on the clutch hub nut. The tusk clutch holder is too thick to fit in the grooves and slips when I try to use a ratchet and socket.

I'll try my impact tomorrow and hope that provides better results but I'm not sure how I'm going to torque it back down during assembly.

You can take a file to it to make it thinner, I've had to do that.
Or you can stick a piece of aluminum in between The clutch basket and main drive gear.
Or a good impact gun will break that nut free no problem.

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4 minutes ago, Four square T said:


You can take a file to it to make it thinner, I've had to do that.
Or you can stick a piece of aluminum in between The clutch basket and main drive gear.
Or a good impact gun will break that nut free no problem.

Take a a look at this video. Maybe the motion pro ones are a bit thinner? Otherwise use an impact:

 

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