Sorry but I have to disagree with pinching the brake hoses. The hoses are high pressure lines. If you clamp down on those, you will damage and weaken them. They may not leak, but they can collapse. I had this before, and it caused the caliper to not release all the way, and drag.
I also believe that you probably have air in the lines. If your prop valve is not leaking then I doubt that would be your problem. I also don't think that a Line Lock leaking internal would give you this problem. I had a truck that had no back brakes. I kept bleeding a little out of the rear wheels. Still no brakes. Finally I picked up a quart bottle of fluid, and used almost all of it just bleeding the rears. Great brakes after that. The method that I now use to bleed them, and seems to work great: Remove each bleeder screw, put some grease on the threads, to prevent air from getting sucked back in. Stick a hose on the bleeder, and stick the hose in a glass jar. I prefer Planters. Slowly pump the pedal until you see no more air. Make sure you don't let the MC run dry, or you have to start all over. Make sure the end of the hose stays submerged under the fluid. Good Luck, and let everyone know what you find.
Brian
P.S. Of course these are all just my opinions, and I could be wrong about everything.