Komatsu 4D98 Series Shop Manual page 56

4. Engine Body
(5.5) Valve rocker arm
Mainly inspect valve head cap contact
surface, inside surface defects and
wear.
Slight surface defects shall be corrected
with an oilstone.
(mm)
Standard Limit
Arm hole diameter
18.50-18.52
18.57
Shaft
O.D. 18.47-18.49
18.44
Clearance
0.01-0.05 0.13
(5.6) Valve rocker arm shaft
Mainly inspect seizure and wear at the
surface in sliding contact with the arm.
The rocker shaft diameter shall be as
specified in (5.5) above.
(5.7) Push rod
Mainly inspect the surface in contact
with the tappet and adjusting screw.
Slight defects shall be corrected with an
oilstone.
Bend limit
0.03 mm or less
(5.8) Valve clearance adjusting screw
Mainly inspect the surface in contact
with the push rod.
Slight defects shall be corrected with an
oilstone.
(5.9)
Rocker arm spring
Mainly inspect surface defects and cor-
rosion.
(6) Valveseat correction
Rocker arm hole diameter
Rocker shaft outside diameter
Push rod bend
- [ NOTICE ]
Always check the oil clearance between the valve and valve guide before correcting
the valve seat. If it exceeds the limit, replace the valve or valve guide first to make the
clearance satisfy the standard. After correction, wash the valve and the cylinder
head sufficiently with diesel oil to remove all grinding powder or compound.
4-8