I've been working on a 91 KDX 250 and after a day of work I split the case. The crank shaft is completely seized and it's extremely hard to find a new crankshaft for this bike unless you buy and OEM one which is like $350. I was wondering if you can put a KX 250 crankshaft of a similar year into the KDX engine. If you have any info please help me out, thanks!

 

Nice, another one of those "obsolete" kawasaki components after I have looked in a couple of parts fiches.

I do not have an answer for you on the cranks. I have found that the kdx was behind the kx in upgrades if any upgrades were to be had.
A crank from a previous kdx would be most likely a better choice.
Clean up what you have first to see where you are at with this. I think that rebuilt cranks may be in the same ball park for price. ( I have not shopped around to confirm that.) Good luck on the project and welcome to KF

 

I've been doing a little research on the part and the crank shaft from the kdx 250 has the exact same part number from the kx's. So it should work shouldn't it?

 

If you found an exact p/n, go for it if you still think that your original is out of specs and needs to be replaced.