2017 YAMAHA WR 250F Owners Manual

CYLINDER AND PISTON
6-36
TIP
• Apply the engine oil to the piston pin.
• Install the piston with the F mark “a” on it
pointing to its intake (front) side.
• Before installing the piston pin clip, cover the
crankcase opening with a cloth to prevent the
clip from falling into the crankcase.
• Install the piston pin clips, so that the clip ends
are 3 mm (0.12 in) “c” or more from the cutout
in the piston.
3. Lubricate:
•Piston
• Piston rings
• Cylinder
4. Offset:
• Piston ring end gap5. Install:
• Cylinder gasket
• Dowel pin
• Cylinder
TIP
• While compressing the piston rings with one
hand, install the cylinder with the other hand.
• Pass the timing chain and timing chain guide
(exhaust side) through the timing chain cavity.
a. Top ring
b. Upper oil ring rail
c. Oil ring expander
d. Lower oil ring rail
1
3
2 a
3 c
a
db
c15
15
15
Cylinder bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
New
T R..

ELECTRIC STARTER
6-37
EAS2GBB262
ELECTRIC STARTER
Removing the starter motor
Order Job/Parts to remove Q’ty Remarks
Exhaust pipe Refer to “ENGINE REMOVAL” on page 6-1.
1 Starter motor 1
For assembly, reverse the disassemble pro-
cedure.
1
12 Nm (1.2 m kgf, 8.7 ft Ibf)T.R.

ELECTRIC STARTER
6-38
Disassembling the starter motor
Order Job/Parts to remove Q’ty Remarks
1 Starter motor front cover 1
2 Starter motor yoke 1
3 Armature assembly 1
4 Starter motor rear cover 1
5 Brush set 2
For assembly, reverse the disassembly pro-
cedure.

ELECTRIC STARTER
6-39
EAS2GBB263CHECKING THE STARTER MOTOR
1. Check:
•Commutator
Dirt  Clean with 600 grit sandpaper.
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
blade that has been grounded to fit the com-
mutator.
TIP
The mica of the commutator must be undercut
to ensure proper operation of the commutator.
4. Measure:
• Armature assembly resistances (commuta-
tor and insulation)
Out of specification  Replace the starter
motor.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Measure the armature assembly resistanc-
es with the pocket tester.b. If any resistance is out of specification, re-
place the starter motor.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
5. Measure:
• Brush length “a”
Out of specification  Replace the brush
set.
6. Measure:
• Brush spring force
Out of specification  Replace the brush
set.
7. Check:
• Gear teeth
Damage/wear  Replace the starter motor. Limit
16.6 mm (0.65 in)
Mica undercut (depth)
1.50 mm (0.06 in)
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
Armature coil
Commutator resistance “1”
0.0189–0.0231 
Insulation resistance “2”
Above 1 M
Limit
3.50 mm (0.14 in)
Brush spring force
3.92–5.88 N (400–600 gf, 14.11–
21.17 oz)

ELECTRIC STARTER
6-40
8. Check:
• Oil seal
Damage/wear  Replace the defective part
(s).
EAS2GBB264ASSEMBLING 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.
ECA
NOTICE
Be careful not to damage the brush during
installation.
3. Install:
• O-ring “1”
• Starter motor yoke “2”
ECA
NOTICE
Install the part that has a smaller step differ-
ence “a” with the magnet of the starter mo-
tor yoke facing the starter motor front
cover.
TIP
Align the match mark “b” on the starter motor
yoke with the match mark “c” on the starter mo-
tor rear cover.4. Install:
• Circlip
•Plain washer “1”
• O-ring “2”
• Washer (starter motor front cover) “3”
• Starter motor front cover “4”
TIP
• For installation, align the projections 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.
5. Install:
•Bolt “1”
• O-ring “2”
TIP
Apply the lithium-soap-based grease on the O-
ring.
New
a1
2
bc
New
New

ELECTRIC STARTER
6-41

CLUTCH
6-42
EAS2GBB265
CLUTCH
Removing the clutch
Order Part name Q’ty Remarks
Engine oilDrain.
Refer to “CHANGING THE ENGINE OIL” on
page 3-17.
Brake pedal Refer to “ENGINE REMOVAL” on page 6-1.
1 Clutch cable 1 Disconnect.
2 Clutch cover 1
3Gasket 1
4 Clutch spring 5
5 Pressure plate 1
6 Push rod 1 1
7 Circlip 1
8Washer 1
9 Bearing 1
10 Ball 1
11 Push rod 2 1
12 Friction plate 1 4
13 Clutch plate 8
New
New
New
2
3 45
(5)
(6)78961011
12
22
1
15
12
13
13
18
1920 17
16
14
13
T.R.
T.R.
T.R.
T.R.
LT
21
72

CLUTCH
6-43
14 Cushion spring 1
15 Friction plate 2 5 Identification color (purple)
16 Clutch boss 1
17 Thrust washer 1
18 Primary driven gear 1
19 Spacer 1
20 Bearing 1
21 Washer 1
22 Push lever shaft 1
For installation, reverse the removal proce-
dure.
Removing the clutch
Order Part name Q’ty Remarks
New
New
New
2
3 45
(5)
(6)78961011
12
22
1
15
12
13
13
18
1920 17
16
14
13
T.R.
T.R.
T.R.
T.R.
LT
21
72