Any body know what size the bleed scres are for the brakes on a '77 CB 750 F? I tried to bleed them tonight and sheered off two of three.

The third will only turn about 1 time around before it sticks so I know it is going to snap. Lots of liquid wrench didn't seem to help.
I am waiting for the Clymers and Hayes manuals I ordered to arrive. Should there be a spacer on the rear wheel between the bracker for the brake and the wheel? I am wondering if my caliper bracket is bent of just missing a piece. It is rubbing on the disk. There is no other damage I can see on the right side other than the tail light doesn't match the other 3.
