Yamaha Wr250r 2008 Manual

 
VALVES AND VALVE SPRINGS 
5-17 
EAS24270 
VALVES AND VALVE SPRINGS 
Removing the valves and valve springs
Order Job/Parts to remove Q’ty Remarks  
Cylinder head Refer to“CYLINDER HEAD” on page 5-14.
1 Valve lifter 4
2 Valve pad 4
3 Valve cotter 8
4 Valve spring retainer 4
5 Valve spring 4
6 Exhaust valve 2
7 Intake valve 2
8 Valve stem seal 4
9 Valve spring seat 4
For installation, reverse the removal proce-
dure.
11
22
33
44
55
6
7 88
99
M
M
M 

 
VALVES AND VALVE SPRINGS 
5-18 
EAS24280 
REMOVING THE VALVES 
The following procedure applies to all of the
valves and related components.
NOTE:
 
Before removing the internal parts of the cylin-
der head (e.g., valves, valve springs, valve 
seats), make sure the valves properly seal.
1. Remove: 
 
Valve lifter “1” 
 
Valve pad “2”
NOTE:
 
Make a note of the position of each valve lifter
and valve pad so that they can be reinstalled in 
their original place.
2. Check: 
 
Valve sealing
Leakage at...

 
VALVES AND VALVE SPRINGS 
5-19 
EAS24290 
CHECKING THE VALVES AND VALVE 
GUIDES 
The following procedure applies to all of the
valves and valve guides.
1. Measure: 
 
Valve-stem-to-valve-guide clearance
Out of specification  
→ 
 Replace the valve
guide.2. Replace: 
 
Valve guide
NOTE:
 
To ease valve guide removal and installation,
and to maintain the correct fit, heat the cylinder 
head to 100  
°  
C (212  
°  
F) in an oven.

 
a. Remove the valve guide with the...

 
VALVES AND VALVE SPRINGS 
5-20
NOTE:
 
After replacing the valve guide, reface the valve 
seat.

 
3. Eliminate: 
 
Carbon deposits
(from the valve face and valve seat)
4. Check: 
 
Valve face
Pitting/wear  
→ 
 Grind the valve face. 
 
Valve stem end
Mushroom shape or diameter larger than the
body of the valve stem  
→ 
 Replace the valve.
5. Measure: 
 
Valve margin thickness “a”
Out of specification  
→ 
 Replace the valve.6. Measure: 
 
Valve stem runout
Out of...

 
VALVES AND VALVE SPRINGS 
5-21

 
a. Apply Mechanic’s blueing dye (Dykem) “b”
onto the valve face.
b. Install the valve into the cylinder head.
c. Press the valve through the valve guide and
onto the valve seat to make a clear impres-
sion.
d. Measure the valve seat width “a”.
NOTE:
 
Where the valve seat and valve face contacted
one another, the blueing will have been re- 
moved.

 
4. Lap: 
 
Valve face 
 
Valve seat
NOTE:
 
After...

 
VALVES AND VALVE SPRINGS 
5-22 
h. Install the valve into the cylinder head.
i. Press the valve through the valve guide and
onto the valve seat to make a clear impres-
sion.
j. Measure the valve seat width “c” again. If the
valve seat width is out of specification, reface
and lap the valve seat.

 
EAS24310 
CHECKING THE VALVE SPRINGS 
The following procedure applies to all of the
valve springs.
1. Measure: 
 
Valve spring free length “a”
Out of specification  
→...

 
VALVES AND VALVE SPRINGS 
5-23 
EAS24320 
CHECKING THE VALVE LIFTERS 
The following procedure applies to all of the
valve lifters.
1. Check: 
 
Valve lifter
Damage/scratches  
→ 
 Replace the valve lift-
ers and cylinder head. 
EAS24340 
INSTALLING THE VALVES 
The following procedure applies to all of the
valves and related components.
1. Deburr: 
 
Valve stem end
(with an oil stone)
2. Lubricate: 
 
Valve stem “1” 
 
Valve stem seal “2”
(with the recommended lubricant)3. Install: 
 
Valve “1” 
...

 
VALVES AND VALVE SPRINGS 
5-24 
5. To fasten the valve cotters “1” onto the valve
stem, lightly tap the valve tip with a soft-face
hammer.
CAUTION:
 
 ECA13800 
Hitting the valve tip with excessive force 
could damage the valve. 
6. Lubricate: 
 
Valve pad “1” 
 
Valve lifter “2”
7. Install: 
 
Valve pad 
 
Valve lifter
NOTE:
 
 
The valve lifter must move smoothly when ro-
tated with a finger. 
 
Each valve lifter and valve pad must be rein- 
stalled in its original position.  
Recommended...

 
CYLINDER AND PISTON 
5-25 
EAS24350 
CYLINDER AND PISTON 
Removing the cylinder and piston
Order Job/Parts to remove Q’ty Remarks  
Cylinder head Refer to“CYLINDER HEAD” on page 5-14.
1 Cylinder 1
2 Dowel pin 2
3 Water pipe 1
4 O-ring 1
5 Cylinder gasket 1
6 Piston pin clip 2
7 Piston pin 1
8 Piston 1
9 Piston ring set 1
For installation, reverse the removal proce-
dure.
1
22
3
45 6
6 7 8 9
E
E
E
T R..10 Nm (1.0 m • kg, 7.2 ft • Ib)  

 
CYLINDER AND PISTON 
5-26 
EAS24380 
REMOVING THE PISTON 
1. Remove: 
 
Piston pin clips “1” 
 
Piston pin “2” 
 
Piston “3”
CAUTION:
 
 ECA13810 
Do not use a hammer to drive the piston pin 
out.
NOTE:
 
 
Before removing the piston pin clip, cover the
crankcase opening with a clean rag to prevent
the piston pin clip from falling into the crank-
case. 
 
Before removing the piston pin, deburr the pis-
ton pin clip’s groove and the piston’s pin bore 
area.
2. Remove: 
 
Top ring 
 
2nd ring 
...