Honda 954 Service Manual page 423

INSPECTION
Check the piston boot, primary cup and secondary
cup for fatigue or damage.
Check the master cylinder and piston for abnormal
scratches.
Measure the master cylinder I.D.
SERVICE LIMIT: 15.925 mm (0.6270 in)
Measure the master cylinder piston O.D.
SERVICE LIMIT: 15.815 mm
(0.6226 in)
HYDRAULIC BRAKE