Komatsu 4D98 Series Shop Manual page 140

9. Starting Motor
b) Measure the depth of the insulating material between commutator segments, and correct if
it is less than 0.2 mm.
Bad
Good
ksaw blade
Hacksaw blade
Commutator
Commutator
Segment mica
&h
Bad
Good
(Under-cutting method)
c) Armature coil continuity and earth tests
Test type Measurement point Normal
Abnormal (cause)
Continuity test Across commutator
Yes None (open circuit)
Earth test
Between commutator None Yes (short-circuiting)
and shaft or armature
Replace if needed.
(Armature coil continuity test) (Armature coil insulation test)
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