Yamaha Wr250r 2008 Manual

 
CYLINDER AND PISTON 
5-27 
d. If out of specification, replace the cylinder,
piston and piston rings as a set.
e. Calculate the piston-to-cylinder clearance
with the following formula.
f. If out of specification, replace the cylinder,
piston and piston rings as a set.

 
EAS24430 
CHECKING THE PISTON RINGS 
1. Measure: 
 
Piston ring side clearance
Out of specification  
→ 
 Replace the piston
and piston rings as a set.
NOTE:
 
Before measuring the piston ring side...

 
CYLINDER AND PISTON 
5-28 
3. Measure: 
 
Piston pin bore diameter “b”
Out of specification  
→ 
 Replace the piston.
4. Calculate: 
 
Piston-pin-to-piston-pin-bore clearance
Out of specification  
→ 
 Replace the piston pin
and piston as a set. 
EAS24450 
INSTALLING THE PISTON AND CYLINDER  
1. Install: 
 
Top ring “1” 
 
2nd ring “2” 
 
Lower oil ring rail “3” 
 
Upper oil ring rail “4” 
 
Oil ring expander “5”
NOTE:
 
Be sure to install the piston rings so that the 
manufacturer’s marks or...

 
CYLINDER AND PISTON 
5-29 
4. Lubricate: 
 
Piston 
 
Piston rings 
 
Cylinder
(with the recommended lubricant)
5. Offset: 
 
Piston ring end gaps
6. Install: 
 
Cylinder
NOTE:
 
 
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. 
Recommended lubricant
Engine oil 
a. Top ring
b. Upper oil ring rail
c. Oil ring expander
d. Lower oil ring rail
e. 2nd ring
f....

 
STARTER MOTOR 
5-30 
EAS24780 
STARTER MOTOR 
Removing the starter motor
Order Job/Parts to remove Q’ty Remarks  
Seat/Air scoop (left/ritht)Refer to “GENERAL CHASSIS” on page 
4-1.
EXUP cable/Exhaust pipe/Muffler Refer to “ENGINE REMOVAL” on page 5-1.
1 Starter motor lead 1 Disconnect.
2 Starter motor 1
For assembly, reverse the disassembly pro-
cedure.
1
2T R..5 Nm (0.5 m • kg, 3.6 ft • Ib) T R..10 Nm (1.0 m • kg, 7.2 ft • Ib)  

 
STARTER MOTOR 
5-31 
Disassembling the starter motor
Order Job/Parts to remove Q’ty Remarks  
1 Starter motor front cover 1
2 Lock washer 1
3 Armature assembly 1
4 Starter motor yoke 1
5 Starter motor rear cover 1
6 Brush holder set 1
For assembly, reverse the disassembly pro-
cedure.
1 2 34 5
6 

 
STARTER MOTOR 
5-32 
EAS24790 
CHECKING THE STARTER MOTOR 
1. Check: 
 
Commutator
Dirt  
→ 
 Clean with 600 grit sandpaper.
2. Measure: 
 
Commutator diameter “1”
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 commuta-
tor.
NOTE:
 
The mica of the commutator must be undercut to 
ensure proper operation of the commutator.
4. Measure: 
...

 
STARTER MOTOR 
5-33 
7. Check: 
 
Gear teeth
Damage/wear  
→ 
 Replace the gear.
8. Check: 
 
Bearing 
 
Oil seal
Damage/wear  
→ 
 Replace the defective part
(s). 
EAS24800 
ASSEMBLING THE STARTER MOTOR 
1. Install: 
 
Brush holder “1”
NOTE:
 
Align the tab on the brush seat with the slot in the 
starter motor rear cover “2”.
2. Install: 
 
Thrust support “1”
NOTE:
 
Align the tab of thrust support with the slot of sta- 
tor motor front cover “2”.
3. Install: 
 
Starter motor yoke “1” 
...

 
CLUTCH 
5-34 
EAS25061 
CLUTCH 
Removing the clutch cover
Order Job/Parts to remove Q’ty Remarks  
Drain the engine oilRefer to “CHANGING THE ENGINE OIL” on 
page 3-11.
Drain the coolantRefer to “CHANGING THE COOLANT” on 
page 3-18.
1 Brake pedal spring 1 Remove it from the frame mounting hook.
2 Water pump housing cover 1
3 Gasket 1
4 Oil cleaner element cover 1
5 Oil cleaner element 1
6 Cover 1
7 Clutch cover 1Remove the clutch cover only if you do not 
remove the primary drive gear.
8 Clutch cover...

 
CLUTCH 
5-35 
For installation, reverse the removal proce-
dure.  
Removing the clutch cover
Order Job/Parts to remove Q’ty Remarks
1
23
45
678
91011
1213 14
14
T R..10 Nm (1.0 m • kg, 7.2 ft • Ib) 
T R..10 Nm (1.0 m • kg, 7.2 ft • Ib) 
T R..10 Nm (1.0 m • kg, 7.2 ft • Ib) 
T R..10 Nm (1.0 m • kg, 7.2 ft • Ib)  

 
CLUTCH 
5-36 
Removing the clutch
Order Job/Parts to remove Q’ty Remarks  
1 Clutch spring 5
2 Pressure plate 1
3 Push rod 1
4 Locknut 1
5 Friction plate 7
6 Clutch plate 6
7 Primary drive gear nut 1
8 Lock washer 1
9 Clutch boss nut 1
10 Lock washer 1
11 Clutch boss 1
12 Thrust washer 1
13 Clutch housing 1
14 Ball 1
15 Clutch push rod 1
16 Primary drive gear 1
For installation, reverse the removal proce-
dure.
23
4
5 (5)1(5)
6
78 910111213 1415
16
E
E
T R..8 Nm (0.8 m • kg, 5.8 ft • Ib) 
T R..8 Nm...