I got this bike, a 78 kz1000, and the brake line was full of dried break fluid. I had to replace the line, and clean out the master cylinder, but still, after all is clear in the master cylinder and the line, I can't get fluid to pump out. Does anyone have any clue what's going on?

 

Does the piston in the M/C actually move?

 

Remove the line from the caliper, and see if it pumps fluid. The caliper may be gunked-up. Also the master cylinder may have a wad up crap hung up in it, if it hasn't been rebuilt any time recently then get a rebuild kit, and overhaul it.