2007-2009 Honda TRX300EX TRX300X service manual, Page 289Get this manual
HYDRAULIC DISC BRAKE master piston piston spring
Clean the master cylinder, reservoir and master piston in clean brake fluid
INSPECTION
Check the master cylinder and master piston for scoring, scratches or damageCheck the piston cups for wear, deterioration or damage
MASTER PISTON
Measure the master cylinder 1.0
SERVICE LIMIT: 12.755 mm (0.5022 in)