Honda TRX450R Service Manual page 217

CYLINDER HEAD/VALVE
Using a 60° interior cutter, remove 1/4 of the exist-
ing valve seat material.
TOOLS:
Interior cutter, 37.5 mm (60° IN) 07780-0014100
Interior cutter, 34 mm (60° EX) 07780-0014700
Cutter holder, 5.5 mm 07781-0010101
Cutter holder, 5.0 mm
(After '05; EX) 07781-0010400
or equivalent commercially available in U.S.A.
Using a 45° seat cutter, cut the seat to the proper
width.
VALVE SEAT WIDTH:
IN: 1.1 - 1.3 mm (0.043 - 0.051 in)
EX: 1.3 - 1.5 mm (0.051 - 0.059 in)
Make sure that all pitting and irregularities are
removed.
OLD SEAT WIDTH
60°
SEAT WIDTH
'04 - 05; INTAKE & EXHAUST SIDE and
After '05; EXHAUST SIDE:
After cutting the seat, apply lapping compound and
engine oil to the valve face, and lap the valve using
light pressure.
After lapping, wash any residual compound off the
cylinder head and valve. Recheck the seat contact
after lapping.
HAND-LAPPING
TOOL
NOTICE
• Excessive lapping pressure may deform or dam-
age the seat.
• Change the angle of lapping tool frequently to
prevent uneven seat wear.
• Do not allow lapping compound to enter the
guides.
After '05; INTAKE SIDE:
After refacing, wash the cylinder head and valve.
NOTICE
Do not lap the intake valves. They are titanium
and have a thin oxide coating. Lapping will dam-
age this coating.
Use the intake valve as a new one.
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