Yamaha TT-R90(T) Owner's Service Manual page 340

ELECTRIC STARTING SYSTEM (TT-R90E)
INSPECTION AND REPAIR
1. Inspect:
Commutator
G
Dirt → Clean it with #600 grit sandpaper.
2. Measure:
Commutator diameter a
G
Commutator wear limit:
16.6 mm (0.65 in)
Out of specification → Replace the
starter motor.
3. Measure:
Mica undercut a
G
Mica undercut:
1.35 mm (0.05 in)
Out of specification → Scrape the mica
to the proper value (a hacksaw blade
can be ground to fit).
NOTE:
The mica insulation of the commutator must be
undercut to ensure proper operation of com-
mutator.
4. Measure:
Armature assembly resistance (com-
G
mutator and insulation)
Out of specification → Replace the
starter motor.
Measurement steps:
Measure the armature assembly resis-
G
tances with the pocket tester.
Pocket tester
YU-3112-C/90890-03112
Armature coil:
Commutator resistance 1
0.018 ~ 0.022 Ω at 20 ˚C (68 ˚F)
Insulation resistance 2
Above 1 MΩ at 20 ˚C (68 ˚F)
If any resistance is out of specification,
G
replace the starter motor.
6 - 13
– +
ELEC