2007-2009 Honda TRX300EX TRX300X service manual, Page 296Get this manual
HYDRAULIC DISC BRAKE Measure the master cylinder 1.0SERVICE LIMIT: 12.755 mm (0.5022 in)
Measure the master piston 0.0SERVICE LIMIT: 12.645 mm (0.4978 in)
ASSEMBLY
Coat the master piston and piston cups with clean brake fluidDo not allow the piston cup lips to turn inside out
Install the spring onto the piston end Install the spring and master piston into the master cylinderApply silicone grease to the piston contacting surface of the push rodBe cerrain the snap Install the push rod assembly and the snap ring into ring is firmly seated the groove in the master cylinderin the groove