I am making slow progress restoring my one owner 1972 DT2.  I am now finding that I can't get the clutch to disengage.  I have made all the adjustment I can, with no help.  The clutch release pulls very hard but never enough to release the clutch.  I have not pulled the clutch apart yet.  I would assume that worn pressure plates or springs would present the opposite result, letting the clutch slip.  What do i check next?

Have you had your engine apart? If not your clutch plates may be stuck you can pull your clutch lever towards the handlebar and zip tie it for a few hours and put your bike in gear and rock your bike back and forward to free the plates

Yep, the plates are stuck. Use the method suggested by HT1Kid. I used a less intelligent method and probably wrecked my friction plates, which I later replaced because they were slipping badly afterwards.

Sounds like worm gear in left case might be stuck/damaged/stripped.

Like Mark said it could be your worm gear, if it looks like the picture below it needs to be replaced.  You can get a replacement from KDI, they make a brass piece that works very well.

 

Thanks for reply.  I will definitely try that and post the results.

The worm gear looks okay but, I may replace it anyway.  Brass seems like it may work better.  It has never worked well.  Meanwhile, I will try HT1kid's suggestion.

Not that this is the issue but I replaced the clutch cable on my DT1 and the difference was incredible. 

No luck so far.  Would it help to partially disassemble the clutch, such as removing the pressure plate, the clutch boss, etc.?

You're right that the cable is not the cause in this case but, being that it is 50 years old, a new one would probably make it work smoother once I get it working.