Yamaha WR250F 2008 Owner's And Service Manual page 212

CHECKING AND REPAIRING THE
STARTER MOTOR
1. Check:
• Commutator
Dirt → Clean with 600 grit sandpa-
per.
2. Measure:
• Commutator diameter "a"
Out of specification→Replace the
starter motor.
Min. commutator diame-
ter:
16.6 mm (0.65 in)
3. Measure:
• Mica undercut "a"
Out of specification → Scrape the
mica to the proper measurement
with a hacksaw blade which has
been grounded to fit the commu-
tator.
Mica undercut:
1.5 mm (0.06 in)
The mica must be undercut to ensure
proper operation of the commutator.
4. Measure:
• Armature assembly resistances
(commutator and insulation)
Out of specification→Replace the
starter motor.
a. Measure the armature assembly
resistances with the pocket tester.
Pocket tester:
YU-3112-C/90890-
03112
ELECTRIC STARTING SYSTEM
Armature assembly:
Commutator resis-
tance "1":
0.0189–0.0231 Ω at 20
°C (68 °F)
Insulation resistance
"2":
Above 1 MΩat 20 °C
(68 °F)
b. If any resistance is out of specifi-
cation, replace the starter motor.
5. Measure:
• Brush length "a"
Out of specification→Replace the
brushes as a set.
Min. brush length:
3.5 mm (0.14 in)
6. Measure:
• Brush spring force
Out of specification→Replace the
brush springs as a set.
Brush spring force:
3.92–5.88 N (400–600
gf, 14.1–21.2 oz)
ASSEMBLING THE STARTER
MOTOR
1. Install:
• Brush spring "1"
• Brush "2"
7-11
2. Install:
• Armature assembly "1"
Install while holding down the
brush using a thin screw driver.
Be careful not to damage the brush
during installation.
3. Install:
• Gasket "1"
• Starter motor yoke "2"
• Install the starter motor yoke with its
groove "a" facing front cover.
• Align the match mark "b" on the
starter motor yoke with the match
mark "c" on the starter motor rear
cover.
4. Install:
• Gasket "1"
• Circlip
• Plain washer "2"
• Washer (starter motor front cover)
"3"
• Starter motor front cover "4"
• For installation, align the projec-
tions on the washer with the slots in
the front cover.
• Align the match mark "a" on the
starter motor yoke with the match
mark "b" on the starter motor front
cover.