Yamaha VK540EF Service Manual page 362

ELECTRICAL STARTING SYSTEM
STARTER MOTOR
Inspection
1. Inspect:
S Commutator (outer surface)
CAUTION:
Lightly grip the armature with a vise.
2. Measure:
S Commutator (diameter)
3. Measure:
S Mica 1 (insulation depth)
4. Measure:
S Armature coil resistance
Inspecting steps:
S Connect the pocket tester for the continuity
S Measure the armature coil resistances.
S If the resistance is incorrect, replace the
7-22
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.
Commutator wear limit a :
27.0 mm (1.06 in)
(between commutator segments)
Out of specification ! Scrape mica to proper
limits.
Use a hacksaw blade 2 that is ground to fit.
Mica undercut limit 3 :
0.6 mm (0.024 in)
(insulation/continuity)
Defect(s) ! Replace starter motor.
check 1 and the insulation check 2 .
Armature coil resistance:
Continuity check 1 :
0.016 Ω
Insulation check 2 :
More than 100 kΩ at 20_C
(68_F)
starter motor.
ELEC
10% at 20_C (68_F)