Not wishing to
**** on your bonfire but those vacuum bleeders don't seem to work on series motors, at least they won't for me. I bought one a while back and had no success with it. It is sounding like your master cylinder is
**** however before condemning it I'd bleed with an eezibleed. I've just changed all of the wheel cylinders and brake shoes on the ambulance...

...and had no dramas using the g-clamping method and eezibleed. The CB master cylinders are trickier than a CV but once bled work fine. The beauty of the eezibleed is it effectively bleeds the system without the master cylinder having to pump, sometimes that can encourage a stubborn one to work. Failing that, I wouldn't bin it. There are companies that will re-sleeve them for around £75 - I'm sure Kev or Parksy posted summat recently about this.