[retro]

You could have a broken or unhooked return spring, a seized wheel cylinder piston, an over-tight or seized adjuster, or even all of the above at the same time under that drum.

First thing is to back off both of the adjusters so you can be sure that the brake shoes are not tight against the drum or too close to the drum for the shoes to clear. There is a hole in the drum that you can push a big flat-bladed screwdriver into to rotate the adjuster star wheels. If they are seized up, spray some PB blaster or similar on them and use the screwdriver blade and a small hammer to try to tap the seized adjuster in either direction until they both turn freely. Work carefully and don't ruin it.

Then try to pull the drum off... you may have to tap on it around the center where the axle comes through it and use two screwdrivers to pry it away from the backer plate. Use some pb blaster on the shaft if it looks rusty there. Don't beat on it hard, don't miss where you aim your hammer or pry on it too hard, else you might ruin something.

If you still can't get the drum off, use some heat from a torch to expand the drum around the axle but again, be careful, and don't get it too hot. You can easily ruin stuff...

 

[retro]

As far as I know there is no wheel cylinder OR rebuild kit available for this bike so if it's hosed then thats the end of the road for this ride unless I'm missing something.

There is no such thing as the end of the road for your ride... or any other ride for that matter. Lots of good used parts are still available for that. You may not need much of anything at all anyway... many times those brake parts just need a lil' careful cleaning and lil' fixing up.

A determined man will always be the sole creator of his own successes, regardless! Hang in there...

 

[retro]

Ya gotta do what ever it takes so I think you are doing fine. Your "slide hammer" idea using the rim was a good idea. If you can figure out a way to get a more effective stroke out of rigging something up similar to that... Nothing wrong with using a puller either. Or a big hammer. Check out the troubles jeepwm69 had with a bike he's working on:
HERE

 

[retro]

I'll do some snooping in a few minutes... Sometimes a grease gun and a grease zerk screwed into the back of the wheel cylinder will get the piston moving... yours sound pretty bad though... sounds like your bearings and seals were already shot too. Tough breaks...

 

[retro]

I see what you mean about fleebay. Nothing but rebuild kits there right now. One seller has the complete backer plates still loaded with the cylinder, adjusters and shoes for $99 OBO and thats it. May have to wait in the weeds for one... unless you can find it local. In the meantime maybe try a grease gun on it with a bit of heat from a torch to expand the cylinder a bit. Careful though, a piston can come out of there like a bullet if its under a lot of force.

 

[retro]

I think you found the solution!! I imagine all of those cylinders would work. The newer Recon cylinders are probably a safer bet though, cause someone already verified the fit on them. The adjuster blocks look pretty close to the same too.

Master cylinder will be a similar deal if you need one... Most of them take the same banjo bolt to hook up the brake line and they all fit a 7/8" handlebar, so whatever you can find cheap will probably work just fine. Thanks for sharing that!

 

[retro]

I got this thread saved along with the one you linked for future reference. Let us know how it turns out.