Checking The Starter Motor - Yamaha WR250R Service Manual

EAS24790

CHECKING THE STARTER MOTOR

1. Check:
Commutator
G
Dirt → Clean with 600 grit sandpaper.
2. Measure:
Commutator diameter "1"
G
Out of specification → Replace the starter
motor.
Limit
27.0 mm (1.06 in)
3. Measure:
Mica undercut "a"
G
Out of specification → Scrape the mica to the
proper measurement with a hacksaw blade
that has been grounded to fit the commuta-
tor.
Mica undercut (depth)
0.70 mm (0.03 in)
NOTE:
The mica of the commutator must be undercut to
ensure proper operation of the commutator.
4. Measure:
Armature assembly resistances (commutator
G
and insulation)
Out of specification → Replace the starter
motor.
MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
a. Measure the armature assembly resistances
with the pocket tester.
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
Armature coil
Commutator resistance "1"
0.004–0.005 Ω at 20°C (68°F)
Insulation resistance "2"
Above 1 MΩ at 20°C (68°F)
b. If any resistance is out of specification, re-
place the starter motor.
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5. Measure:
Brush length "a"
G
Out of specification → Replace the brushes
as a set.
Limit
3.50 mm (0.14 in)
6. Measure:
Brush spring force
G
Out of specification → Replace the brush
springs as a set.
Brush spring force
7.16–9.52 N (25.77–34.27 oz)
(730–971 gf)
5-32
STARTER MOTOR