Engine Seized - 13 KX250F

[BugsySiegals]

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.

 

 

[Wild Alaskan]

You are going to have to take it apart and find out what else is damaged, if that's from the crank the crank is 100% for sure toast.

[allrightythen]

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 August 27, 2017 by allrightythen

[Zanestroud]

I'm not helpful at all but is this a common problem for these bikes?

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[BOAB]

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.

[BugsySiegals]

I assume if was the lower connecting rod bearing that it would have gouged up the crank and I cannot reuse it?

Is it worth buying a remanufactured OEM crank like this one here ... https://www.ebay.com/itm/322147092202

[mlatour]

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

 

[BugsySiegals]

What would I look for on the cases to determine if they need replacement? Just the areas where the bearings seat?

[allrightythen]

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

[BugsySiegals]

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.

[BOAB]

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.

[BugsySiegals]

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?

[BugsySiegals]

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.

[MatthewMCRepair]

Here is a rebuild video that covers your engine.

Tool list: https://www.howtomotorcyclerepair.com/kx250ftopbottomrebuild/

 

 

[MatthewMCRepair]

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:

 

[BugsySiegals]

Here is a rebuild video that covers your engine.
Tool list: https://www.howtomotorcyclerepair.com/kx250ftopbottomrebuild/
 
 

Thanks, unfortunately he wants money for the remaining 2 videos but I did find another video that was good enough for the bottom end.

[BugsySiegals]

I bought a Milwaukee 2763-22 M18 1/2" Inch Impact Wrench and it took the stubborn nuts off without hesitation ... https://www.amazon.com/dp/B00GFUA7FC/ref=cm_sw_r_cp_api_U5ERzbZSX29A0

[BugsySiegals]

I've disassembled everything but the bearings. The connecting rod is very stiff and gritty feeling so the bearing must be shot. Can I assume the crank is garbage or should I find a way to open it up and find out?

[BugsySiegals]

With regards to the engine case, I noticed it had various writing on it like you'd find from a scrap yard. Would that exist on the original engine?

[BugsySiegals]

I also noticed the case had gasket sealant around the inside of edges which didn't seem to even go on the faces of the case, is this normal?