2006 Honda TRX680 Rincon Factory Service Manual, Page 422Get this manual
BRAKE SYSTEM INSPECTION Check the master cylinder and master piston for scoring, scratches or damageCheck the piston cups and oil seal for wear, deterioration or damageMeasure the master cylinder I.DSERVICE LIMIT: 14.055 mm (0.5333 in) Measure the master cylinder piston O.DSERVICE LIMIT: 13.945 mm (0.5490 in)
ASSEMBLY
Coat the master piston, piston cups and oil seal with clean DOT brake fluidInstall the oil seal into the master cylinderInstall the spring onto the piston endDo not allow the piston cup lips to turn inside out
MASTER CYLINDER