Kubota M108S, Workshop Manual

Page: 176 / 523

1-S53
M108S, WSM ENGINE
Correcting Valve and Valve Seat
NOTE
■
• Before correcting the valve and seat, check the valve stem
and the I.D. of valve guide section, and repair them if
necessary.
• After correcting the valve seat, be sure to check the valve
recessing.
1) Correcting Valve
1. Correct the valve with a valve refacer.
2) Correcting Valve Seat
1. Slightly correct the seat surface with a 1.0 rad (60 °) (intake
valve) or 0.79 rad (45 °) (exhaust valve) valve seat cutter.
2. Resurface the seat surface with a 0.52 rad (30 °) valve seat cutter
to intake valve seat and with a 0.26 rad (15 °) valve seat cutter to
exhaust valve seat so that the width is close to specified valve
seat width.
3. After resurfacing the seat, inspect for even valve seating, apply a
thin film of compound between the valve face and valve seat, and
fit them with a valve lapping tool.
4. Check the valve seating with prussian blue. The valve seating
surface should show good contact all the way around.
W10283500
Valve face angle
Factory
spec.
IN.
1.0 rad
60 °
EX.
0.79 rad
45 °
Valve seat width
Factory
spec.
IN.
1.6 to 2.0 mm
0.063 to 0.078 in.
EX.
2.3 to 2.6 mm
0.091 to 0.10 in.
Valve seat angle
Factory
spec.
IN.
1.0 rad
60 °
EX.
0.79 rad
45 °
(1) Valve Seat Width
(2) Identical Dimensions (A) Check Contact
(B) Correct Seat Width
(C) Check Contact
(a) 0.26 rad (15 °) or 0.52 rad (30 °)
(b) 0.79 rad (45 °) or 1.0 rad (60 °)
(c) 0.52 rad (30 °) or 0.26 rad (15 °)
KiSC issued 06, 2007 A