Yamaha YZ 2019 Series, Owner'S Service Manual

Page: 235 / 398

ELECTRIC STARTER
5-36
EAM30106
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 commutator.
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.
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a. Measure the armature assembly resistances
with the digital circuit tester.
b. If any resistance is out of specification, re-
place the starter motor.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
5. Measure:
• Brush length “a”
Out of specification

Replace the brush set.
6. Measure:
•
Brush spring force
Out of specification

Replace the brush set.
Commutator diameter limit
16.6 mm (0.65 in)
Mica undercut (depth)
1.50 mm (0.06 in)
Digital circuit tester (CD732)
90890-03243
Model 88 Multimeter with tachom-
eter
YU-A1927
Armature coil resistance
0.0189–0.0231 
Insulation resistance
Above 1 M 
1. Armature resistance
2. Insulation resistance
Brush overall length limit
3.5 mm (0.14 in)
Brush spring force
3.92–5.88 N (400–600 gf, 14.11–
21.17 oz)
1
2