Yamaha WR450F(T) Owner's Service Manual page 680

ELECTRIC STARTING SYSTEM
INSPECTION AND REPAIR
1. Check:
2. Measure:
3. Measure:
NOTE:
The mica must be undercut to ensure proper
operation of the commutator.
4. Measure:
• Measure the armature assembly resis-
• If any resistance is out of specification,
6 - 14
• Commutator
Dirt → Clean with 600 grit sandpaper.
• Commutator diameter a
Out of specification → Replace the
starter motor.
Min. commutator diameter:
16.6 mm (0.65 in)
• Mica undercut a
Out of specification → Scrape the mica to
the proper measurement with a hacksaw
blade which has been grounded to fit the
commutator.
Mica undercut:
1.5 mm (0.06 in)
• Armature assembly resistances (commu-
tator and insulation)
Out of specification → Replace the
starter motor.
tances with the pocket tester.
Pocket tester:
YU-03112-C/90890-03112
Armature assembly:
Commutator resistance 1:
0.0117 ~ 0.0143 Ω at 20 °C
(68 °F)
Insulation resistance 2:
Above 1 MΩ at 20 °C (68 °F)
replace the starter motor.
– +
ELEC