This story is my experience verbatim:
80 brakes seem to be frustrating to a lot of people.
I had it power flushed this morning, and they were unable to get the "mush" out as well. Seems like the Master Cylinder is the next likely part to be replaced. Does it make sense that the design of the 80 brakes would cause the LSPV to be the circuit most affected by a MC leak? I haven't read about a lot of 80 series MC problems, but maybe by letting it run dry during this process I dislodged a "fluid seal" and introduced a small air leak in the O-ring?
Has anyone else had to replace their 80 MC? Looks like I have a few choices: Marlin sells a big bore MC for the 80's, MAF has AISIN brand units, and of course there's OEM.