TOHATSU BFT75A Service Manual page 401

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CYLINDER HEAD
Use the 30° – 32° and 60° cutters to narrow and adjust
the valve seat so that it contacts the middle of the valve
face.
The 30° – 32° cutter removes material from the top
edge.
The 60° cutter removes material from the bottom edge.
Be sure that the width of the finished valve seat is within
specification.
STANDARD:
IN:
EX:
Make a light pass with the 45° cutter to remove any
possible burrs at the edges of the seat.
After resurfacing the seats, inspect for even valve
seating.
Apply Prussian Blue compound or erasable felt-tipped
marker ink to the valve faces. Insert the valves, and
then lift them and snap them closed against their seats
several times. Be sure the valve does not rotate on the
seat. The seating surface, as shown by the transferred
marking compound, should have good contact all the
way around.
Lap the valves into their seats, using a hand valve
lapper (LIL-21100; commercially available) [1] and
lapping compound.
• To avoid severe engine damage, be sure to remove
all lapping compound from the cylinder head before
assembly.
Recheck the seat contact after lapping (page 14-34).
Check the valve installation height (page 14-34).
14-42
0.85 – 1.15 mm (0.033 – 0.045 in)
1.25 – 1.55 mm (0.049 – 0.061 in)
CONTACT TOO HIGH
CONTACT TOO LOW
OLD SEAT
WIDTH
32°
OLD SEAT
WIDTH
60°
IN: 0.85 – 1.15 mm
(0.033 – 0.045 in)
EX: 1.25 – 1.55 mm
(0.049 – 0.061 in)
[1]