Yamaha RS90K Manuel D'atelier page 648

ELECTRICAL STARTING SYSTEM
Inspection
1. Inspect:
CAUTION:
Lightly grip the armature with a vise.
2. Measure:
3. Measure:
4. Measure:
Inspecting steps:
• Connect the pocket tester for the continuity
• Measure the armature coil resistances.
• If the resistance is incorrect, replace the starter
8-14
• Commutator (outer surface)
Dirty → Clean with #600 grit sandpaper 1.
Hold the armature in a vise 2 and copper or
aluminium plate 3.
• 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)
• 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)
• Armature coil resistance
(insulation/continuity)
Defect(s) → Replace the starter motor.
check 1 and the insulation check 2.
Armature coil resistance:
Continuity check:
0.008 ~ 0.010 Ω at 20 °C (68 °F)
Insulation check:
More than 100 kΩ at 20 °C (68 °F)
motor.
– +
ELEC