2005-2009 Honda TRX400EX/TRX400X Service Manual, Page 275Get this manual
HYDRAULIC DISC BRAKE Measure the master cylinder 1.0SERVICE LIMIT: 12.75 mm (0.502 in)
Measure the master piston .0 SERVICE LIMIT: 12.65 mm (0.498 in)
ASSEMBLY
Coat the master piston and piston cups ith clean brake fluid Do flOt allow fhe p'STOn cup lips to fum IIlslde OUI
Install the primary cup onto the spring Install the spring and master iston into th master cylinderApply silicone grease to th piston contacting surface of the push rod