Checking The Starter Motor - Yamaha MBK MW125 2014 Service Manual

EAS30325

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.
Commutator diameter
22.0 mm (0.87 in)
Limit
21.0 mm (0.83 in)
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 commutator.
Mica undercut (depth)
1.50 mm (0.06 in)
TIP
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.
▼ ▼▼▼
a. Measure the armature assembly resistances
with the digital circuit tester.
a
2
b. If any resistance is out of specification, re-
place the starter motor.
▲ ▲▲▲
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
springs as a set.
5-54
ELECTRIC STARTER
▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼
Digital circuit tester
90890-03174
Model 88 Multimeter with ta-
chometer
YU-A1927
Armature coil resistance
0.0315–0.0385 Ω
Insulation resistance "2"
No continuity (Above 1 MΩ at 20
°C (68 °F))
1
▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲
Brush overall length
9.5 mm (0.37 in)
Limit
3.50 mm (0.14 in)
a
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