3-28 ENGINE
45˚
15˚
Valve seat
EXHAUST
VALVE SEAT WIDTH
• Coat the valve seat with prussian blue uniformly. Fit the valve
and tap the coated seat with the valve face in a rotating man-
ner, in order to obtain a clear impression of the seating contact.
In this operation, use the valve lapper to hold the valve head.
• The ring-like dye impression left on the valve face must be con-
tinuous – without any break. In addition, the width of the dye
ring, which is the visualized seat “width”, must be within the
following specification:
" Valve seat width W
Standard: 0.9 – 1.1 mm (0.035 – 0.043 in)
% 09916-10911: Valve lapper set
If either requirement is not met, correct the seat by servicing it as
follows:
VALVE SEAT SERVICING
The valve seats for intake and exhaust valves are machined to
four different angles. The seat contact surface is cut at 45°.
INTAKE EXHAUST
15° N-121
30° N-128
45° N-128 N 122
60° N-111
NOTE:
The valve seat contact area must be inspected after each cut.
% 09916-21111: Valve seat cutter set
09916-22430: Valve seat cutter (N-128)
60˚
45˚
Valve seat
INTAKE
30˚
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