Well, it's got me stumped why the back brakes won't bleed. I've got new brake lines, bleed nipples, new slave cylinder kit installed (correctly) new hose from the master cup to the cylinder, new rubbers in the back brake pistons. I've filled the cylinder to the top and reconnected the brake hose, tested the stroke of the ram, I'm getting fluid out of both nipples and no air bubbles, and still there's no pressure on the brake lever. No leaks anywhere, but I did notice the bleed nipples weep a little if not tightened up fully.
I've wedged the brake lever down overnight, to see if any air bubbles in the system will make their way out, no luck.
any ideas people?
Check if there's a tiny (1mm) relief port in the master cylinder that might have been blocked. Exactly the same symptoms as you describe are found when that port is blocked in the front master.