Yamaha RS90RK, Service Manual

Page: 648 / 841

8-14
– +
ELEC
ELECTRICAL STARTING SYSTEM
Inspection
1. Inspect:
• Commutator (outer surface)
Dirty
→
Clean with #600 grit sandpaper
1
.
Hold the armature in a vise 2 and copper or
aluminium plate
3
.
CAUTION:
Lightly grip the armature with a vise.
2. Measure:
• Commutator diameter
a
Measure the diameter
a
of the commutator at
points where the brush comes in contact.
Out of specification
→
Replace the starter
motor.
Commutator diameter wear limit:
27.5 mm (1.08 in)
3. Measure:
• Mica undercut (insulation depth)
a
(between commutator segments)
Out of specification
→
Scrape mica
1
to
proper limits.
Use a hacksaw blade
2
that is ground to fit.
Mica undercut:
1.5 mm (0.059 in)
4. Measure:
• Armature coil resistance
(insulation/continuity)
Defect(s)
→
Replace the starter motor.
Inspecting steps:
• Connect the pocket tester for the continuity
check
1
and the insulation check
2
.
• Measure the armature coil resistances.
• If the resistance is incorrect, replace the starter
motor.
Armature coil resistance:
Continuity check:
0.008 ~ 0.010
Ω
at 20 °C (68 °F)
Insulation check:
More than 100 k
Ω
at 20 °C (68 °F)