If plates are stuck, removing pressure plate will give you access to the stack so you can separate the frictions from the steels.  No need to mess with hub.

The clutch released when I took off the pressure plate.   However, when I put the pressure plate and springs back on, the clutch now slips no matter how I adjust it.   I removed it again and the springs measure short of standard by 3 mm.  The clutch plates seem okay.  I guess the stuck plates were disguising the real problem.   Now to find some new springs.

Yes 3 mm is a bunch. I think standard is 36.4 mm and Yamaha says replace if 2 or more mm short. I’ve ordered new springs for my DTs and RTs and even new ones rarely measured 36.4.  I’ve used Barnett heavy duty springs when I can find them for my application. For my 360s and 400s I’ve gone to Barnett frictions as well. You’ll put maybe $150 into your clutch pack but I haven’t had any slipping by doing that.

Partzilla has them Clutch springs

Clutch plates can look OK but when they are old can slip. Suggest new plates and springs. The new plates from Yamaha # 5Y1-16331-01 are an improved design with wider tabs. If you use heavier springs it may put more strain on the nylon spiral on the clutch push actuator. The brass replacement from KDI is able to hold up to the increased tension. Also the cable sheath can be worn and compressed. Also I've found some new aftermarket cables to be harder to pull.

I am still going through a learning curve with my DT3 clutch. Seems to be the Achilles heel of some of these models to me.
I have discovered the hard way that the brass worm gear from KDI MUST be pressed onto the actuator shaft in exactly the correct orientation or the clutch will not work right...You get one shot to get it right. It seems impossible to get off again  . There is really good  clutch fix if you search for this topic but it takes some tools and some skills using a more common clutch actuator.  The actuators for the DT1-3 models seem to be very rare and very expensive if can you find one.

This is just my experience with the Yamaha clutches on bikes from this era and I have a way of making something easy more challenging that it should be be; my disclaimer.
Good luck, take your time and take the advise of the folks here.

Sorry you put your clutch actuator on wrong, that sucks big time I'm sure. When I did mine I marked where the original was with a sharpie so I could get it back on the exact same way. I wasn't sure if it made a difference but didn't want to take a chance.

Have you thought about cutting it off with a dremel? Sucks that you'd have to buy another but has to be cheaper and easier then trying to find a used one.

If it makes you feel better I've made some pretty costly mistakes learning about these bikes, mostly because of not paying attention and getting in a hurry...

Thanks AirborneSilva.  I got them from PartZilla and now the clutch engages well.  Apparently though, I have multiple layers of problems.  Now, it will not disengage again.  I am now seeing that the clutch release never moves the plunger.  I plan to replace the worm gear next.   I guess this is what I should expect from a 50 year-old bike that's had hard use.

When I got my DT2 about 9 months ago I could pull the clutch in then put it in gear and it would jump a tiny bit like everything was good to go but then when I let the clutch out I got nothing! I went ahead and replaced pretty much everything, cable, worm gear (from KDI), clutch fibers/plates and pressure plate springs. I probably didn't have to replace all that but figured do it once and be done with it!

NOTE: When replacing the worm gear mark with a sharpy exactly where the old worm gear fitted against the "push lever assembly" # 21 in the parts diagram you can find on partzilla.

Definitely need to replace the worm gear actuator.   It is not obvious to me how best to remove it without damaging something else.  My Clymer manual is no help.   Does it screw out?  Does the push lever need to be removed from the inside by prying it out/