2004-2009 Honda TRX450R/TRX450ER Service Manual, Page 420Get this manual
HYDRAULIC BRAKE INSPECTION Check the master cylinder and master piston for scoring, scratches or damageCheck the piston cups for wear, deterioration or damage
ASSEMBLY
Coat the master piston and piston cups with clean DOT brake fluidInstall the spring onto the piston endDo not allow the Install the spring and master piston into the master piston cup lips to cylinderturn inside outInstall the push rod into the master cylinder