Yamaha WR250F 2016, Owner'S Service Manual

Page: 266 / 428

ELECTRIC STARTER
6-37
EAS2GB7263
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 com-
mutator.
TIP
The mica of the commutator must be undercut
to ensure proper operation of the commutator.
4. Measure:
• Armature assembly resistances (commuta-
tor and insulation)
Out of specification

Replace the starter
motor.
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a. Measure the armature assembly resistanc-
es 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 brush
set.
6. Measure:
• Brush spring force
Out of specification

Replace the brush
set.
Limit
16.6 mm (0.65 in)
Mica undercut (depth)
1.50 mm (0.06 in)
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
Armature coil
Commutator resistance “1”
0.0189–0.0231

Insulation resistance “2”
Above 1 M

Limit
3.50 mm (0.14 in)
Brush spring force
3.92–5.88 N (400–600 gf, 14.11–
21.17 oz)