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Cylinder Head
Valve Seat Reconditioning
If the valve guides are worn (see page 6-43), replace
them (see page 6-44) before cutting the valve seats.
1. Renew the valve seats in the cylinder head using a
valve seat cutter.
2. Carefully cut a 45° seat, removing only enough
material to ensure a smooth and concentric seat.
3. Bevel the upper edge of the seat with a 30° cutter
and the lower edge of the seat with a 60° cutter.
Check the width of the seat and adjust accordingly.
4. Make one more very light pass with the 45° cutter
to remove any possible burrs caused by the other
cutters.
After resurfacing the seat, inspect for even valve
seating: Apply Prussian Blue compound (A) to the
valve face. Insert the valve in its original location in
the head, then lift it and snap it closed against the
seat several times.
The actual valve seating surface (B)
r
as shown by
the blue compound, should be centered on the seat.
• If it is too high (closer to the valve stem), you
must make a second cut with the 60° cutter to
move it down, then one more cut with the 45°
cutter to restore seat width.
• If it is too low (closer to the valve edge), you must
make a second cut with the 30° cutter to move it
up, then one more cut with the 45° cutter to
restore seat width.
NOTE: The final cut should always be made with
the 45° cutter.
Valve Seat Width:
Standard (New): 1.25-1.55 m m
(0.049-0.061 in.)
Service Limit:
2.00 m m (0.079 in.)
6-46
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Troubleshooting
