Buddy has a 77 Super Glide that rear brakes wont release fully after applying brakes. He has replaced the master cylinder twice, Rear brake line twice, Caliper three times, tore linkage loose to make sure nothing was binding up. If you crack the bleeder the pressure backs off and brakes release. I still think its a master cylinder issue with calipers holding pressure. This is driving him crazy. Can some one clue us in or heard of anyone that has had simular isses? We even went so far as to make sure brake line didnt have any bendsor extreme bends in it. The really puzzling thing is one of the master cylinders we took off he gave to another buddy and it worked fine on his bike. By replacing every thing that we have I dont see or I dont know where to go from there. The only thing we havent replaced is the rotor. Any help at all would really be appreciated.

Scott

 

okay not 100% on the set on on the 77 super glides. I am assuming it has a link rod going back to the master cylinder from the brake pedal. If so you need to slacken this off so there is free play. It sounds like the rod is pressing slightly on the end of the piston so the pressure isnt full released and the fluid return to the master cylinder.
Back the rod off a few turns and see what happens

 

Its set up with a rod going from pedal to linkage on case, then another rod going from lever to master cylinder. We have adjusted both rods until there was 1/2" play in pedal and it still does it.

Scott

 

hum next one then is to take the caliper off. pump it up. losen the banjo bolt at the master cylinder and see if you can push the piston back and see if the fluid comes out the master cylinder end of the line. As you said the old one works fine on someone esles bike I get a feeling its in the line somewhere, maybe the pressure switch union or a bit of the liner is acting like a none return valve. I have assumed you have tried a new line on there ?
Hum other silly thing to check is that the bolts in the banjosare the right one and all the holes match up, theres a damned sight more pressur ebeing aplied by the master cylinder when it push the fluid out then when it comes back, make sure you have some rag wrpaed aorudn the end of the union when you break it open as if there is pressure in the line it can spray out.

 

Has this bike been converted from drum to disk brakes by any chance?

Cheers... Ben.