Kubota M5040, Workshop Manual

Page: 181 / 559

1-S55
M5040, M6040, M7040, WSM ENGINE
Correcting Valve and Valve Seat
NOTE
Q
• 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 0.785 rad (45 °) valve seat
cutter.
2. Resurface the seat surface with a 0.262 rad (15 °) valve seat
cutter 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 valve lapping tool.
4. Check the valve seating with prussian blue. The valve seating
surface should show good contact all the way around.
W10283500
Free Length and Tilt of Valve Spring
1. Measure the free length ( B ) with vernier calipers. If the
measurement is less than the allowable limit, replace it.
2. Put the spring on a surface plate, place a square on the side of
the spring, and check to see if the entire side is contact with the
square. Rotate the spring and measure the maximum (
A ). If the
measurement exceeds the allowable limit, replace.
3. Check the entire surface of the spring for scratches. Replace it,
if any.
W1063303
Valve face angle
(Intake and exhaust)
Factory spec.
0.785 rad
45 °
Valve seat width
(Intake and exhaust)
Factory spec.
3.3 to 3.6 mm
0.1299 to 0.1417 in.
Valve seat angle
(Intake and exhaust)
Factory spec.
0.785 rad
45 °
(1) Valve Seat Width
(2) Identical Dimensions (A) Check Contact
(B) Correct Seat Width
(C) Check Contact
(a) 0.262 rad (15 °)
(b) 0.785 rad (45 °)
(c) 0.523 rad (30 °)
Tilt ( A ) Allowable limit
1.0 mm
0.039 in.
Free length ( B )
Factory spec.
35.1 to 35.6 mm
1.3819 to 1.4016 in.
Allowable limit
34.6 mm
1.3622 in.
(A) Tilt (B) Free length
KiSC issued 06, 2008 A