This is how to rebuild the master cylinder found on many mid 70's Honda Motorcycles with disc brake. Rebuild kit is available here:
Models include: 1973 CB350G, 1973 - 1976 CB360T, CB400F, CB450 K3 - K7, CB500T, CB500 K1, CB550.
Common Motor Collective is our community workshop in Houston, Texas. www.common-motor.com