Honda GL1800 Service Manual page 270

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.
Using a 45° seat cutter, remove any roughness or
irregularities from the seat.
TOOLS:
Valve seat cutter, 33 mm (IN)
Valve seat cutter, 29 mm (EX)
Cutter holder, 5.0 mm
or equivalent commercially available in U.S.A.
Using a 32° flat cutter, remove 1/4 of the existing
valve seat material.
TOOLS:
Flat cutter, 35 mm (IN)
Flat cutter, 33 mm (EX)
Cutter holder, 5.0 mm
or equivalent commercially available in U.S.A.
Using a 60° interior cutter, remove 1/4 of the exist-
ing valve seat material.
TOOLS:
Interior cutter, 30 mm (IN/EX)
Cutter holder, 5.0 mm
or equivalent commercially available in U.S.A.
07780-0010800
07780-0010300
07781-0010400
07780-0012300
07780-0012900
07781-0010400
07780-0014000
07781-0010400
CYLINDER HEAD/VALVE
OUGHNESS
8-21