Parts Inspection And Measurement - Komatsu 4D98 Series Shop Manual

4. Engine Body
(5)
(5.1)
l
Different stem seals are provided for the intake and exhaust valves. Do not confuse them
since those for exhaust valves are marked with yellow paint.
l
After assembling the intake/exhaust valve, stem seal, valve spring, seat, and cotter, tap the
head of the valve stem lightly for settling.
l
Do not forget to install the valve cap.
Parts Inspection and measurement
Cylinder head
Clean the cylinder head, mainly the combustion surface, valve seats and intake/exhaust
ports, remove carbon deposit and bonding agent, and check the surface state.
(a) Appearance check
Check mainly discoloration and crack.
If crack is suspected, perform color check.
(b) Combustion surface distortion
Apply a strait-edge in two diagonal di-
rections and on four sides of the cylin-
der head, and measure distortion with
a thickness gage.
0-m-d
0.05 or less
Limit
0.15
(c)Valve sink
Measure with the valve inserted to
the cylinder head.
(mm\
Standard Limit
4TNE94.98 Intake 0.5-0.7 1 .o
Exhaust 0.6-0.8 1.1
4TNE106 (T) Intake 0.7-0.9 1.2
Exhaust 0.9-1.1 1.4
Distortion at combustion surface
Valve
Depth micrometer
Valve sink
depth
Valve sinking depth
4-5