Honda CBR125R, Owner'S Manual

Page: 208 / 430

CYLINDER HEAD/VALVES
8-20
• Contact area (too high or too low area):
– Reface the valve seat.
Inspect the width of the valve seat.
The valve seat contact should be within the speci-
fied width and even all around the circumference.
If the valve seat width is not within specification,
reface the valve seat.
VALVE SEAT REFACING
• Follow the refacing manufacturer’s operating
instructions.
• Reface the valve seat whenever the valve guide
has been replaced.
• Be careful not to grind the seat more than neces-
sary.
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
°
inner cutter.
TOO HIGH
TOO LOW
STANDARD: 0.90 – 1.10 mm (0.035 – 0.043 in)
SERVICE LIMIT: 1.50 mm (0.059 in)
VALVE SEAT
CONTACT WIDTH
32
°
60
°
45
°
32
°
CONTACT TOO HIGH
60
°
OLD SEAT
WIDTH
OLD SEAT
WIDTH
CONTACT TOO LOW