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...

 
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...

 
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...

 
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...

 
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....

 
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:...

 
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...

 
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...

 
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...