Refacing - Honda NSS250S Manual

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Inspect the valve seat face.
The valve seat contact should be within the speci-
fied width and even all around the circumference.
STANDARD: 0.90 – 1.10 mm (0.035 – 0.043 in)
SERVICE LIMIT: 1.5 mm (0.06 in)
If the valve seat width is not within specification,
reface the valve seat (page 9-17).

REFACING

• Reface the valve seat whenever the valve guide
has been replaced.
• Be careful not to grind the seat more than neces-
sary.
Valve seat cutters/grinders or equivalent valve seat
refacing equipment is recommended to correct
worn valve seats.
• Follow the refacing manufacture's operating
instructions.
If the contact area is too high on the valve, the seat
must be lowered using a 32° flat cutter.
If the contact area is too low on the valve, the seat
must be raised using a 60° interior cutter.
CYLINDER HEAD/VALVES
VALVE SEAT
CONTACT WIDTH
SEAT CUTTER
32°
CONTACT TOO HIGH
CONTACT TOO LOW
45°
60°
OLD SEAT
WIDTH
32°
OLD SEAT
WIDTH
60°
9-17