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 the valve seat  
→ 
 Check the valve
face, valve seat, and valve seat width.
Refer to “CHECKING THE VALVE SEATS”
on page 5-20.

 
a. Pour a clean solvent “a” into the intake and
exhaust ports.
b. Check that the valves properly seal.
NOTE:
 
There should be no leakage at the valve seat 
“1”.

 
3. Remove: 
 
Valve cotters “1”
NOTE:
 
Remove the valve cotters by compressing the
valve spring with the valve spring compressor 
“2”.
4. Remove: 
 
Valve spring retainer “1” 
 
Valve spring “2” 
 
Valve “3” 
 
Valve stem seal “4” 
 
Valve spring seat “5”
NOTE:
 
Identify the position of each part very carefully 
so that it can be reinstalled in its original place.
1
2
 
Valve spring compressor
90890-04019
YM-04019
1a
12 
						

							 
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 valve guide
remover “1”.
b. Install the new valve guide with the valve
guide installer “2” and valve guide remover
“1”.
c. After installing the valve guide, bore the valve
guide with the valve guide reamer “3” to ob-
tain the proper valve-stem-to-valve-guide
clearance.  
Valve-stem-to-valve-guide clearance =
Valve guide inside diameter  
“ 
a 
” 
 -
Valve stem diameter  
“ 
b 
” 
Valve-stem-to-valve-guide clear-
ance
Valve-stem-to-valve-guide clear-
ance (intake)
0.010 
– 
0.037 mm (0.0004 
– 
0.0015
in)
Limit
0.080 mm (0.0032 in)
Limit
0.08 mm (0.0032 in)
Valve-stem-to-valve-guide clear-
ance (exhaust)
0.025 
– 
0.052 mm (0.0010 
– 
0.0020
in)
Limit
0.100 mm (0.0039 in)
Limit
0.10 mm (0.004 in)
1
2
4
5
3
1
2 
						

							 
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 specification   
→  
 Replace the valve.
NOTE:
 
 
When installing a new valve, always replace
the valve guide. 
 
If the valve is removed or replaced, always re- 
place the oil seal. 
EAS24300 
CHECKING THE VALVE SEATS 
The following procedure applies to all of the
valves and valve seats.
1. Eliminate: 
 
Carbon deposits
(from the valve face and valve seat)
2. Check: 
 
Valve seat
Pitting/wear  
→  
 Replace the cylinder head.
3. Measure: 
 
Valve seat width “a”
Out of specification  
→  
 Replace the cylinder
head. 
Valve guide remover ( 
ø 
4.5)
90890-04116
YM-04116
Valve guide installer ( 
ø 
4.5)
90890-04117
YM-04117
Valve guide reamer ( 
ø 
4.5)
90890-04118
YM-04118
Valve margin thickness
Valve margin thickness D (intake)
1.15 
– 
1.45 mm (0.0453 
– 
0.0571 in)
Limit
1.00 mm (0.0394 in)
Valve margin thickness D (ex-
haust)
0.85 
– 
1.15 mm (0.0335 
– 
0.0453 in)
Limit
0.70 mm (0.0276 in) 
Valve stem runout
0.010 mm (0.0004 in)
Valve seat width
Valve seat width C (intake)
0.90 
– 
1.10 mm (0.0354 
–  
0.0433 in)
Valve seat width C (exhaust)
0.90 
– 
1.10 mm (0.0354 
–  
0.0433 in) 
						

							 
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 replacing the cylinder head or replacing the
valve and valve guide, the valve seat and valve 
face should be lapped.
CAUTION:
 
 ECA32D1012 
This model uses titanium intake valves.
Titaium valves that have been used to lap the
valve seats must not be used. Always re- 
place lapped valves with new valves.
NOTE:
 
 
When replacing the cylinder head, replace the
valves without lapping the valve seats and
valve faces. 
 
When replacing the valves or valves guides,
use new valves to lap the valve seats, and then 
replace them with new valves.

 
a. Apply a coarse lapping compound “a” to the
valve face.
CAUTION:
 
 ECA13790 
Do not let the lapping compound enter the
gap between the valve stem and the valve 
guide. 
b. Apply molybdenum disulfide oil onto the
valve stem.
c. Install the valve into the cylinder head.
d. Turn the valve until the valve face and valve
seat are evenly polished, then clean off all of
the lapping compound.
NOTE:
 
For the best lapping results, lightly tap the valve
seat while turning the valve back and forth be- 
tween your hands.
e. Apply a fine lapping compound to the valve
face and repeat the above steps.
f. After every lapping procedure, be sure to
clean off all of the lapping compound from the
valve face and valve seat.
g. Apply Mechanic’s blueing dye (Dykem) “b”
onto the valve face.
a 
						

							 
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  
→ 
 Replace the valve
spring.2. Measure: 
 
Compressed valve spring force “a”
Out of specification   
→  
 Replace the valve
spring.
3. Measure: 
 
Valve spring tilt “a”
Out of specification   
→  
 Replace the valve
spring.  
Valve spring free length
Free length (intake)
36.03 mm (1.42 in)
Limit
34.23 mm (1.35 in)
Free length (exhaust)
36.03 mm (1.42 in)
Limit
34.23 mm (1.35 in) 
a. Compressed valve spring force
b. Installed length 
Installed compression spring
force (intake)
147.00  
–  
169.00 N (33.05  
–  
37.99
lbf) (14.99  
–  
17.23 kgf)
Installed compression spring
force (exhaust)
147.00  
–  
169.00 N (33.05  
–  
37.99
lbf) (14.99  
–  
17.23 kgf)
Installed length
31.00 mm (1.22 in)
Spring tilt limit
Spring tilt (intake)
2.5   
°  
/1.6 mm
Spring tilt (exhaust)
2.5   
°  
/1.6 mm 
						

							 
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” 
 
Spring seat “2” 
 
Valve stem seal “3” 
 
Valve spring “4” 
 
Valve spring retainer “5”
(onto the cylinder head)
NOTE:
 
 
Make sure each valve is installed in its original
place. Refer to the following embossed marks. 
 
Install the valve springs with the larger pitch “a” 
facing up.
4. Install: 
 
Valve cotters “1”
NOTE:
 
Install the valve cotters by compressing the
valve spring with the valve spring compressor 
“2” and the valve spring compressor attachment. 
Recommended lubricant
Molybdenum disulfide oil 
a. Larger pitch
b. Smaller pitch 
Valve spring compressor
90890-04019
YM-04019 
						

							 
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 lubricant
Molybdenum disulfide oil
12
M
1 2 
						

							 
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 
 
Oil ring
NOTE:
 
When removing a piston ring, open the end gap
with your fingers and lift the other side of the ring 
over the piston crown. 
EAS24390 
CHECKING THE CYLINDER AND PISTON 
1. Check: 
 
Piston wall (Sidewall) 
 
Cylinder wallVertical scratches  
→  
 Rebore or replace the
cylinder, and replace the piston and piston
rings as a set.
2. Measure: 
 
Piston-to-cylinder clearance

 
a. Measure cylinder bore “D” with the cylinder
bore gauge.
NOTE:
 
Measure cylinder bore “D” by taking side-to-side
and front-to-back measurements of the cylinder. 
Then, find the average of the measurements.
b. If out of specification, rebore or replace the
cylinder, and replace the piston and piston
rings as a set.
c. Measure piston skirt diameter “P” with the mi-
crometer.
1 23
 
Cylinder bore “D”
77.000  
–  
77.010 mm (3.031  
–  
3.032
in)
Limit
77.100 mm (3.035 in)
Taper limit “T”
0.05 mm (0.002 in)
Out of round limit
0.05 mm (0.002 in) 
“D” = maximum of D 
1
 
–  
D 
6
 
“T” = (maximum of D 
1
 
 or D 
2
 
) - (maximum of D 
5
 
 or D 
6
 
)
a. 12 mm (0.47 in) from the bottom edge of the pis-
ton
aP