We have been putting together the front brake set-up for the 750 for quite a while now. I've been saving up the pictures to do a smooth and coherent write-up about it.
The master cylinder is a salvage yard special off a late model Kawasaki sport bike of some sort. 7/8th bars and 10mm banjo fittings. No idea on the bore, but it should work.
The caliper is from a 800/1500 Vulcan I believe. It doesn't fit a the '82(?) Honda front end.
Take some measurements to make a plate.
Mark the aluminum plate.
Hacked out with a bandsaw.
Another mock up.
Mark the caliper bolt holes.
Fly cut 0.100 inch off the surface and tap the holes on the fork side.
Another mock-up and another 0.065 inch surfaced off.
Getting there, but we need bolts.
The rotor is pretty well centered up between the pads. Real good for mostly guessing.
Problably going to cut off this radius to clean it up a bit.
This master cylinder is nasty on the inside.
Suck it dry and clean with brake cleaner.
Looks good. We have brake line, but no new banjo washer so we'll have to hold off filling/bleeding/testing the front brake.