2008 YAMAHA WR 250F Owners Manual

7-8
ELECTRIC STARTING SYSTEM
2. Inspect:• Rubber part "a"
Tears/damage →Replace.

7-9
ELECTRIC STARTING SYSTEM
REMOVING THE STARTER MOTOROrder Part name Q'ty Remarks Exhaust pipe Refer to "REMOVING THE EXHAUST PIPE
AND SILENCER" section in the CHAPTER 3.
1 Starter motor 1

7-10
ELECTRIC STARTING SYSTEM
DISASSEMBLING THE STARTER MOTOROrder Part name Q'ty Remarks1 Starter motor front cover 1
2 Washer (starter motor front cover) 1
3 Gasket 2
4 Starter motor yoke 1
5 Armature assembly 1
6 Starter motor rear cover 1
7 Brush 2
8 Brush spring 2

7-11
ELECTRIC STARTING SYSTEM
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.
3. Measure: • Mica undercut "a"
Out of specification →Scrape the
mica to the proper measurement
with a hacksaw bl ade which has
been grounded to fit the commu-
tator.
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. 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.
6. Measure: • Brush spring forceOut of specification →Replace the
brush springs as a set.
ASSEMBLING THE STARTER
MOTOR
1. Install: • Brush spring "1"
•Brush "2" 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.
Min. commutator diame-
ter: 16.6 mm (0.65 in)
Mica undercut: 1.5 mm (0.06 in)
Pocket tester: YU-3112-C/90890-
03112
Armature assembly:
Commutator resis-
tance "1":0.0189–0.0231 Ω at 20
°C (68 °F)
Insulation resistance
"2":
Above 1 M Ωat 20 °C
(68 °F)
Min. brush length: 3.5 mm (0.14 in)
Brush spring force: 3.92–5.88 N (400–600
gf, 14.1–21.2 oz)

7-12
ELECTRIC STARTING SYSTEM
5. Install:• Gasket
•Bolt "1"
• O-ring "2"
Apply the lithium soap base grease
on the O-ring.

7-13
CHARGING SYSTEM
CHARGING SYSTEM
INSPECTION STEPS
If the battery is not charged, use the following inspection steps.
*1 marked: Refer to "CHECKING TH E FUSE" section in the CHAPTER 3.
*2 marked: Refer to "CHECKING AND CHARGIN G THE BATTERY" section in the CHAPTER 3.
• Remove the following parts before inspection.
1. Seat
2. Fuel tank
• Use the following special tools in this inspection.
*1 Check fuse. No good→Replace fuse and check wire harness.
OK ↓
*2 Check battery. No good→Recharge or replace.
OK ↓
Check each coupler and wire connection. No good →Repair or replace.
OK ↓
Check charging voltage. OK→ Charging system is good.
No good ↓
Check AC magneto. (Charging coil) No good→Replace.
OK ↓
Replace rectifier/regulator.
Pocket tester: YU-3112-C/90890-03112

7-14
CHARGING SYSTEM
CHECKING THE COUPLERS AND
LEADS CONNECTION
1. Check:• Couplers and leads connection
Rust/dust/looseness/short-circuit
→ Repair or replace.
CHECKING THE CHARGING
VOLTAGE
1. Start the engine.
2. Inspect: • Charging voltageOut of specification →If no failure
is found in checking the source
coil resistance, replace the rectifi-
er/regulator.
3. Inspect: • Charging coil resistanceOut of specification →Replace.
Tester (+) lead
→Red lead "1"
Tester (-) lead →Black lead "2"
Charging voltage Tester se-
lector posi- tion
14.0–15.0 V at 5,000 r/ min DCV-20
Tester (+) lead →White lead "1"
Tester (-) lead →Ground "2"
Charging
coil resis- tance Tester se-
lector posi- tion
0.288–0.432 Ω at 20 °C
(68 °F) Ω × 1

7-15
THROTTLE POSITION SENSOR SYSTEM
THROTTLE POSITION SENSOR SYSTEM
INSPECTION STEPS
If the throttle position sensor will not operate, use the following inspection steps.
Use the following special tools in this inspection.
Check entire ignition system for connection. No good →Repair or replace.
OK ↓
Check throttle position sensor.(Throttle position
sensor coil) No good
→
Replace.
OK ↓
Check CDI unit.(Throttle position sensor input
voltage) No good
→
Replace.
Pocket tester:
YU-3112-C/90890-03112