Honda CRF450R 2009 Service Manual page 288

CYLINDERIPISTON
10·12
Apply engine oil to a new O-ring and instal! it to the
water hose joint groove.
Set the waler hose joint to Ihe cylinder.
Install and lighten Ihe bolts securely.
Install Ihe cam chain guide by aligning its tabs with the
grooves in the cylinder and guide end with Ihe groove in
Ihe crankcase.
Inslalithe cylinder head (page 9-30).