I'm creating this thread to document this modification to my 1978 CB750 Super Sport as I know how much trouble the rear master cylinders can be if they have been allowed to deteriorate over the years.
So after two rebuilds of this damn thing, the second one working for about 200 miles before it started binding and leaking brake fluid again, I've decided to finally ditch it. I've ordered a modern, CBR master cylinder off ebay. You can find these all over and they look very similar the the old Super Sport CB750 cylinders:
I've also ordered some aluminum plate stock off Amazon to cut and shape a mounting bracket. The modern cylinder's mounting holes are straight up and down, but the old cb's are in a diagonal placement across the cylinder. My idea is to simply make a little plate that will fit in-between the cylinder and the frame so it's still mounted via two sturdy holes. I then should just need to trim a little height off the bracket that mounts to the foot pedal (or not have to trim it at all if I'm lucky) and finally have a reliable master cylinder.
I will update this thread with photos and results in case anyone else has had nothing but trouble with their old master cylinder and wants to attempt this mod. If it fails, well maybe I'll leave it up too for others to learn from my mistakes haha.
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