Yamaha Wr250r 2008 Manual

							 
CAMSHAFT 
5-7 
REMOVING THE  CAMSHAFT
Order Job/Parts to remove Q’ty Remarks  
1 Timing mark accessing screw 1
2 Crankshaft end cover 1
3 Timing chain tensioner assembly 1
4 Camshaft cap 1
5 Dowel pin 2
6 Camshaft (IN) 1
7 Camshaft (EX) 1
8 Camshaft sprocket (IN) 1
9 Camshaft sprocket (EX) 1
For installation, reverse the removal proce-
dure.
1
23 4
56
78
9
M
M
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..24 Nm (2.4 m • kg, 17 ft • Ib) 
E
E 
						

							 
CAMSHAFT 
5-8 
EAS23800 
REMOVING THE CAMSHAFT 
1. Remove: 
 
Crankshaft end cover 
 
Timing mark accessing screw
2. Align: 
 
TDC on the generator rotor
(mark on the crankcase cover)

 
a. Turn the crankshaft counterclockwise.
b. When piston is at TDC on the compression
stroke, align the mark “a” on the generator ro-
tor with the mark “b” on the crankcase cover.
NOTE:
 
TDC on the compression stroke can be found
when the camshaft lobes are turned away from 
each other.

 
3. Remove: 
 
Cylinder head cover
4. Loosen: 
 
Camshaft sprocket bolt
5. Remove: 
 
Timing chain tensioner assembly 
 
Gasket
6. Remove: 
 
Camshaft cap bolts  
 
Camshaft cap
CAUTION:
 
 ECA32D1006 
To prevent damage to the cylinder head,
camshafts or camshaft caps, loosen the
camshaft cap bolts in satages and in order 
from 1 to 8. 
7. Remove: 
 
Intake camshaft “1”  
 
Exhaust camshaft “2” 
NOTE:
 
To prevent the timing chain from falling into the 
crankcase, fasten it with a wire to it. 
EAS23840 
CHECKING THE CAMSHAFT 
1. Check: 
 
Camshaft lobes
Blue discoloration/pitting/scratches  
→  
 Re-
place the camshaft.
2. Measure: 
 
Camshaft lobe dimensions “a” and “b”
Out of specification  
→  
 Replace the camshaft.
a
b
246 81 3 57
1 2 
						

							 
CAMSHAFT 
5-9 
3. Measure: 
 
Camshaft runout
Out of specification  
→ 
 Replace.4. Measure: 
 
Camshaft-journal-to-camshaft-cap clearance
Out of specification   
→  
 Measure the camshaft
journal diameter.

 
a. Install the camshaft into the cylinder head
(without the dowel pins and camshaft caps).
b. Position a strip of Plastigauge® “1” onto the
camshaft journal as shown.
c. Install the dowel pins and camshaft caps.
NOTE:
 
 
Tighten the camshaft cap bolts in the order of
the embossed numbers on the camshaft cap. 
 
Do not turn the camshaft when measuring the 
camshaft journal-to-camshaft cap clearance.
d. Remove the camshaft caps and then mea-
sure the width of the Plastigauge® “1”.  
Camshaft lobe dimension limit
Intake A
34.550 
– 
34.650 mm 
(1.3602 
– 
1.3642 in)
Limit
35.450 mm (1.3957 in)
Intake B
25.953 
– 
26.053 mm 
(1.0218 
– 
1.0257 in)
Limit
25.853 mm (1.0178 in)
Exhaust A
34.850 
– 
34.950 mm 
(1.3720 
– 
1.3760 in)
Limit
34.750 mm (1.3681 in)
Exhaust B
25.986 
– 
26.086 mm 
(1.0231 
– 
1.0270 in)
Limit
25.886 mm (1.0191 in)
Camshaft runout limit
0.015 mm (0.00059 in) or less 
Camshaft-journal-to-cam-
shaft-cap clearance
0.028  
–  
0.062 mm (0.0011  
–  
0.0024
in)
Limit
0.08 mm (0.0031 in)
Camshaft cap bolts
10 Nm (1.0 m•kg, 7.2 ft•lb)
1
TR.. 
						

							 
CAMSHAFT 
5-10

 
5. Measure: 
 
Camshaft journal diameter “a” 
Out of specification  
→ 
 Replace the camshaft.
Within specification  
→ 
 Replace the cylinder
head and the camshaft caps as a set. 
EAS23870 
CHECKING THE TIMING CHAIN AND 
CAMSHAFT SPROCKET 
1. Check: 
 
Timing chain “1”
Damage/stiffness  
→ 
 Replace the timing
chain and camshaft and camshaft sprocket
as a set.
2. Check: 
 
Camshaft sprocket
More than 1/4 tooth wear “a”  
→ 
 Replace the
camshaft sprocket and the timing chain as a
set. 
EAS23960 
CHECKING THE TIMING CHAIN 
TENSIONERS  
The following procedure applies to both of the
timing chain tensioners.
1. Check: 
 
Timing chain tensioner
Cracks/damage   
→  
 Replace.

 
a. Using a finger, push and insert timing chain
tensioner rod “1” into the timing chain
tensioner housing.
NOTE:
 
Push the timing chain tensioner rod in direction
“a”, and turn the timing chain tensioner body “2” 
in direction “b” until it stops.
b. Keep pressing the timing chain tensioner rod,
mount clip “3” into groove “4”, and lock the
timing chain tensioner rod.
c. Push the timing chain tensioner rod in direc-
tion “c”.
d. Make sure that the timing chain tensioner rod
can smoothly move out from the timing chain
tensioner housing in direction “d”. If not
smooth, replace the timing chain tensioner
assembly.  
Camshaft journal diameter
21.959 
– 
21.972 mm (0.864 
– 
0.865
in)
1
 
a. 1/4 tooth
b. Correct
1. Timing chain roller
2. Camshaft sprocket
a
b1
2
b
a
2
1 
						

							 
CAMSHAFT 
5-11

 
EAS32D1001 
CHECKING THE DECOMPRESSION 
SYSTEM 
1. Check: 
 
Decompression system

 
a. Check that the decompressor lever pin “1”
projects from the camshaft.
b. Check that the decompressor cam “2” moves
smoothly.

 
EAS24000 
INSTALLING THE CAMSHAFTS 
1. Install: 
 
Exhaust camshaft “1” 
 
Intake camshaft “2”
NOTE:
 
 
Stamp line “a” of the camshaft sprocket must
locate in the position as shown. 
 
Temporarily tighten the camshaft sprocket 
bolts.2. Install: 
 
Intake camshaft sprocket 
 
Exhaust camshaft sprocket

 
a. Turn the crankshaft counterclockwise.
b. When piston is at TDC on the compression
stroke, align the mark “a” on the generator ro-
tor with the mark “b” on the crankcase cover.
c. Install the timing chain onto both camshaft
sprockets and then install the exhaust cam-
shaft onto the cylinder head first.
NOTE:
 
Locate mark “c” of exhaust system camshaft
chain sprocket “1” and mark “d” of intake system
camshaft chain sprocket “2” in the same position
at the end of cylinder head as shown. This is the 
Top Dead Center (TDC).
CAUTION:
 
 ECA13740 
Do not turn the crankshaft when installing
the camshaft(s) to avoid damage or improp- 
er valve timing.
Camshaft sprocket bolt
24 Nm (2.4 m•kg, 17 ft•lb)
43cd
1
2
TR..
1
2
a
a
b
a 
						

							 
CAMSHAFT 
5-12

 
3. Install: 
 
Dowel pin 
 
Camshaft cap 
 
Camshaft cap bolts
NOTE:
 
 
Lubricate the camshaft cap bolt threads with
engine oil. 
 
Finger tighten the camshaft cap bolts.
4. Tighten: 
 
Camshaft cap bolts
NOTE:
 
Tighten the camshaft cap bolts in the order of 
the embossed numbers on the camshaft cap.
CAUTION:
 
 ECA13730 
The camshaft cap bolts must be tightened
evenly or damage to the cylinder head, cam- 
shaft caps, and camshafts will result. 
5. Install: 
 
Timing chain tensioner

 
a. Using a finger, push and insert timing chain
tensioner rod “1” into the timing chain
tensioner housing.
NOTE:
 
Push the timing chain tensioner rod in direction
“a”, and turn the timing chain tensioner body “2” 
in direction “b” until it stops.
b. Keep pressing the timing chain tensioner rod,
mount clip “3” into groove “4”, and lock the
timing chain tensioner rod.
c. In the status of step “b”, install the rod assem-
bly in the cylinder block.
NOTE:
 
Always use a new gasket. 
Camshaft cap bolt
10 Nm (1.0 m•kg, 7.2 ft•lb)
1 2
cd
TR..
 
Timing chain tensioner bolt
10 Nm (1.0 m•kg, 7.2 ft•lb)
246 81 3 57
b
a
2
1
43cd
TR.. 
						

							 
CAMSHAFT 
5-13 
d. Unlock the camshaft chain tensioner by turn-
ing the crankshaft counterclockwise, and ten-
sion the timing chain.

 
6. Turn: 
 
Crankshaft
(several turns counterclockwise)
7. Check: 
 
The TDC mark of rotor, and the mark of
crankshaft case cover

 
a. Turn the crankshaft counterclockwise.
b. When the piston is in the compression pro-
cess, align TDC mark “a” of the rotor with
mark “b” of crankshaft case cover.
NOTE:
 
You can check the TDC in compression process 
when the camshaft robes face outward. 
 
Punch mark on the camshaft
Check the matching of stamp line “c” of the
camshaft punch mark timing chain sprocket
and the cylinder head end.
Out of alignment  
→ 
 Reinstall.
Refer to the installation steps above.

 
8. Measure: 
 
Valve clearance
Out of specification  
→ 
 Adjust.Refer to “ADJUSTING THE VALVE CLEAR-
ANCE” on page 3-4.
a
b
cc 
						

							 
CYLINDER HEAD 
5-14 
EAS24100 
CYLINDER HEAD 
Removing the cylinder head
Order Job/Parts to remove Q’ty Remarks  
Camshaft Refer to“CAMSHAFT” on page 5-6.
Hose (thermostat cover) Refer to“THERMOSTAT” on page 6-4.
Coolant temperature sensor coupler
Thermostat
Air induction pipeRefer to“AIR INDUCTION SYSTEM” on 
page 7-9.
1 Cylinder head assembly 1
2 Cylinder head gasket 1
3 Dowel pin 2
For installation, reverse the removal proce-
dure.
1
2
33
E
E
M
M
T R..40 Nm (4.0 m • kg, 29 ft • Ib) 
T R..10 Nm (1.0 m • kg, 7.2 ft • Ib) 
E 
						

							 
CYLINDER HEAD 
5-15 
EAS24130 
REMOVING THE CYLINDER HEAD 
1. Remove: 
 
Cylinder head bolts “1” (M6 
× 
60) 
 
Cylinder head bolts “2” (M10 
× 
154) 
 
Cylinder head bolts “3” (M10 
× 
140)
NOTE:
 
Gradually loosen bolts “a” to “f” in this sequence 
in several times. 
EAS24160 
CHECKING THE CYLINDER HEAD 
1. Eliminate: 
 
Combustion chamber carbon deposits
(with a rounded scraper)
NOTE:
 
Do not use a sharp instrument to avoid damag-
ing or scratching: 
 
Spark plug bore threads 
 
Valve seats
2. Check: 
 
Cylinder head
Damage/scratches  
→ 
 Replace. 
 
Cylinder head water jacket
Mineral deposits/rust  
→ 
 Eliminate.
3. Measure: 
 
Cylinder head warpage
Out of specification  
→ 
 Resurface the cylinder
head.

 
a. Place a straightedge “1” and a thickness
gauge “2” across the cylinder head.
b. Measure the warpage.
c. If the limit is exceeded, resurface the cylinder
head as follows.
d. Place a 400 
–  
600 grit wet sandpaper on the
surface plate and resurface the cylinder head
using a figure-eight sanding pattern.
NOTE:
 
To ensure an even surface, turn the cylinder 
head several times.
e. After resurfacing, out of specification  
→  
 Re-
place the cylinder head.

 
EAS24230 
INSTALLING THE CYLINDER HEAD 
1. Install: 
 
Cylinder head gasket “1” 
 
Dowel pins “2” 
Cylinder head warpage
0.05 mm (0.002 in)
c
f d e
ba 3
3
12
2
1
New 
						

							 
CYLINDER HEAD 
5-16 
2. Install: 
 
Cylinder head
NOTE:
 
Pass the timing chain through the timing chain 
cavity.
3. Tighten: 
 
Cylinder head bolts (M10 
× 
140 )“1” 
 
Cylinder head bolts (M10 
× 
155)“2” 
 
Cylinder head bolts (M6 
× 
60 )“3”
NOTE:
 
 
Lubricate the cylinder head bolts with engine
oil. 
 
Tighten the cylinder head bolts in the proper
tightening sequence as shown and torque 
them in two stages. 
Cylinder head bolt (M10)
40 Nm (4.0 m•kg, 29 ft•lb)
Cylinder head bolt (M6)
10 Nm (1.0 m•kg, 7.2 ft•lb)
M
M
New
4
4
4
12
2
TR..
d
a c b
ef13
1
2