With the exception of the slotted clutch side shaft for the auto lube pump, will  these and a 75 MX 400 Crank interchange?
Im beginning to work on an MX 400 , and the crank is siezed...
A friend has a running DT for CRAZY CHEAP...It's beat up and an ugly rust bucket, wrong tank, no lights, and no oil pump...
Since I'm going to completely rebuild the MX engine, thought the DT crank may work.
To elaborate, the DT actually has both case halves damaged.....and JB welded to crap...
The MX case halves are pristine.....
I'll be completely rebuilding the MX top to bottom...
The DT crank is still in spec with good end and side play, so you can see where my thoughts are taking me
I'm picking up the DT for $50... hahaha..
The MX I got In a bartering situation for some electrical work.

Thoughts?
 

I think you'll be telling 'us'. But guessing a bit i wonder if the clutch cover is stepped in that close that you might need to remove the sticky out bit so just be careful there. Could be differently balanced because its capable of a lot higher revs than the DT. All guesses on my behalf but if it fits then yeah a lot cheaper than rebuilding yours. If you had a press at home you could swap the rod & pin over into the YZ wheels.

Pretty sure the clutch side crankwheel is the same part on both models? 

Rod length could be different?  But I'm pretty sure they are the same.  Just can't hurt to check.

MX had a different radius machined on the ignition-side stub if I remember correctly...  there was a bulletin about the crank bearing radius I think...  but doubt that would be a problem.

Have you actually checked the DT crank rod "wobble" as per manual?  Any rust at all near the big end?  Runout is good?  From the sound of that engine it's a little surprising that crank is in good shape.  Not that it can't be.  Just that getting a crank rebuilt is not that great an expense and using one from a beat up engine might not be worth the risk?