Honda CBR650RA Shop Manual page 273

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VALVE SEAT INSPECTION/REFACING
INSPECTION
Disassemble the cylinder head (page 10-12).
Clean the intake and exhaust valves thoroughly to
remove carbon deposits.
Apply a light coat of Prussian Blue to the valve seats.
Tap the valve against the valve seat several times using
a hand-lapping tool [1], without rotating the valve to
make a clear pattern.
Remove the valve and inspect the valve seat face.
The valves cannot
be ground. If the
The valve seat contact should be within the specified
valve face is
width and even all around the circumference.
burned, badly worn
STANDARD:
or if it contacts the
seat unevenly,
SERVICE LIMIT: 1.5 mm (0.06 in)
replace the valve.
If the valve seat width is not within specification, reface the valve seat (page 10-15).
Inspect the valve seat face for:
• Damaged face:
– Replace the valve and reface the valve seat
• Uneven seat width:
– Bent or collapsed valve stem; Replace the valve and reface the valve seat
• Contact area (too low or too high):
– Reface the valve seat
0.90 – 1.10 mm (0.035 – 0.043 in)
CYLINDER HEAD/VALVES
[1]
SEAT WIDTH
10-15