Leaking tiliton series 75 master cylinders

[Barnsnake]

The Tilton 75 series have unplated aluminum bores. They do wear, especially if the thrust is not exactly straight down the bore. If there is a considerable angle they will wear quickly and eventually get sufficiently out of round that they leak past the piston.

CNC Brakes makes bolt-in replacements in either stainless-lined-aluminum or steel. They've worked well in my experience.