Yamaha YZ450FN 2022, Owner'S Service Manual, Page: 230 / 366

ELECTRIC STARTER
5-44
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
Install the brush holder using the screws “a”.
2. Install:
• Starter motor rear cover “1”
•
O-ring
• Starter motor yoke “2”
TIP
Install the starter motor rear cover with its projec-
Mica undercut (depth)
2.40 mm (0.09 in)
Digital circuit tester (CD732)
90890-03243
Model 88 Multimeter with tachom-
eter
YU-A1927
Brush overall length limit
5.5 mm (0.22 in)
Brush spring force
4.80–7.20 N (489–734 gf, 17.28–
25.92 oz)
1
a
a
2
2
Ne w