Great question — answering as the UphillTech team:
So I believe the issue here is that I did not roll the diaphragm across the lever brake fluid reservoir to push any air out. I initially placed the diaphragm straight down and trapped air that subsequently pumped through the system on my first ride. I don't think I ever needed to replace the master cylinder during this process but the rebuild of the caliper with a full cleaning of the pistons was definitely probably purposeful. I did replace the seals but not sure that was needed. A big part of the bleeding process for me is that my pistons were quite stuck, its all about working the pistons. For my case, no matter what I did, I had a piston that will come out faster than the other pistons....
Full answer by Brian Ogden: https://bicycles.stackexchange.com/a/97482 (CC BY-SA 4.0).
Need it done for your business? UphillTech.
