2004-2009 Honda TRX450R/TRX450ER Service Manual, Page 232Get this manual
CYLINDERPISTON After '05: Disconnect the breather hose from cylinderBREATHER HOSE
PISTON REMOVAL
Place clean shop Remove the piston pin clip with plierstowel over the Push the piston pin out of the piston and connecting crankcase to rod, and remove the pistonprevent the clip from falling into the crankcase