2004-2009 Honda TRX450R/TRX450ER Service Manual, Page 412Get this manual
HYDRAULIC BRAKE Remove the boot from the master cylinder and master piston
Remove the snap ring using the special toolTOOL: Snap ring pliers 07914-SA50001
SNAP RING PLIERS Remove the master piston and springClean the master cylinder, reservoir and master piston in clean brake fluidSPRING