ELECTRIC STARTER
5-37
EAS24790
CHECKING THE STARTER MOTOR
1. Check:
● Commutator
Dirt → Clean with 600 grit sandpaper.
2. Measure:
● Commutator diameter “a”
Out of specification → Replace the starter
motor.
3. Measure:
● Mica undercut “a”
Out of specification → Scrape the mica to the
proper measurement with a hacksaw blade
that has been grounded to fit the commuta-
tor.
NOTE:
The mica of the commutator must be undercut to
ensure proper operation of the commutator.
4. Measure:
● Armature assembly resistances (commutator
and insulation)
Out of specification → Replace the starter
motor.
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a. Measure the armature assembly resistances
with the pocket tester.
b. If any resistance is out of specification, re-
place the starter motor.
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5. Measure:
● Brush length “a”
Out of specification → Replace the brushes
as a set.
6. Measure:
● Brush spring force
Out of specification → Replace the brush
Limit
27.0 mm (1.06 in)
Mica undercut (depth)
0.70 mm (0.03 in)
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
Digital circuit tester
90890-03174
Model 88 Multimeter with tachom-
eter
YU-A1927
Armature coil
Commutator resistance “1”
0.0015–0.0025 Ω at 20°C (68°F)
Insulation resistance “2”
Above 1 MΩ at 20°C (68°F)
Limit
4.00 mm (0.16 in)
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