Yamaha WR250FM 2021, Owner'S Service Manual

Page: 246 / 404

ELECTRIC STARTER
5-46
EAM30106
CHECKING THE STARTER MOTOR
1. Check:
•
Commutator
Dirt

Clean with 600 grit sandpaper.
2. 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.
3. Check:
•
Armature assembly
a. Connect the digital circuit tester to the ar-
mature coil and check the continuity.
b. If there is no continuity, replace the starter
motor.
4. Measure:
•
Brush length “a”
Out of specification

Replace the brush set.
5. Measure:
• Brush spring force
Out of specification

Replace the brush set.
6. Check:
•
Gear teeth
Damage/wear

Replace the starter motor.
7. Check:
• Oil seal
Damage/wear

Replace the defective
part(s).
EAM30107
ASSEMBLING THE STARTER MOTOR
1. Install:
•
Brush spring “1”
•
Brush “2”
TIP
Align the corner of brush terminal “a” with groove
“b” and fit them together.
2. Install:
•
Armature assembly “1”
Install while holding down the brush using a
thin screw driver.
Mica undercut (depth)
1.50 mm (0.06 in)
Digital circuit tester (CD732)
90890-03243
Model 88 Multimeter with tachom-
eter
YU-A1927
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)
a
b
1
1
2
2