MZ/MuZ Riders

After taking my 2002 Baggie with around 3,500 miles on it for its first ride is over 6 months, my rear brake now barely works. Pressing it down till it stops gave only a little braking. Before, the pedal would move more than I am used to, but it would lock up the wheel if you stood on it.
The fluid was brown, but full. Trying to get it to pump out the old fluid gave only a little coming out of the bleeder. I put a syringe on it and couldn't pull the fluid through it. I put an air hose on the bleeder, and it didn't want to push the fluid back. I disconnected it at the master cylinder, and could get a little air movement. I then disconnected the line from the caliper, and hardly any air would blow through when hooked to the bleeder again.

I know there are check valves, but I thought they were all in the MC, not the caliper. Pumping the master with the hose disconnected from the caliper does nothing. No pressure, no fluid movement or draining at all.

First off, does anyone know where the problem is? Second, I would love to put something else on there, but doing a search here, it doesn't appear to have a direct replacement. Also at this point, I am not sure if the problem is the MC or the caliper. I think the MC should pump fluid when pumped, and it doesn't now. Although before I took it all apart, I could get a little fluid to come out, and then it would stop. Nothing close to draining the reservoir.

Any ideas, or source for better parts?

one problem with brakes is they get adjusted wrong

do make sure the pedal returns all the way to its resting point and lets the master cylinder piston return all the way
if it does not return all the way the inlet is blocked that lets fluid in from the tank
also take the system apart and flush out all the old fluid
use brake fluid as the cleaner as other stuff just contaminates the system

brake fluid loves water if you let a can of it set with the lid off it will suck up water and ruin very fast
like in a few hours
systems should be flushed clean and refilled ever couple years
the pucks in the caliper may require a bit of work if they got stuck
plastic does not like brake fluid keep away from the bike
speedo faces hate the brake fluid and will turn foggie old suzuki bikes in the 1970's were bad about that
most bikes still are
dave