Yamaha RX10K Supplementary Service Manual page 366

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