engine YAMAHA WR 250F 2015 Manual Online

ENGINE REMOVAL
6-8
5. Install:
• Spark arrester gasket
• Spark arrester
Insert the spark arrester into the muffler and
align the bolt holes.
• Tail pipe gasket
• Spark arrester bolts
6. Install:
• Muffler cap
TIP
First tighten the two screws “a” located horizon-
tally apart, and then tighten the others.
EAS2GB2234CHECKING THE SILENCER AND EXHAUST
PIPE
1. Check:
•Gasket “1”
Damage  Replace.
EAS2GB2235INSTALLING THE ENGINE
1. Install:
• Engine “1”
Install the engine from the right side.
• Pivot shaft “2”• Engine mounting bolt (lower side) “3”
• Front engine bracket “4”
• Engine bracket bolt (front side) “5”
• Engine mounting bolt (front side) “6”
• Upper engine bracket “7”
• Engine bracket bolt (upper side) “8”
• Engine mounting bolt (upper side) “9”
TIP
Apply molybdenum disulfide grease to the pivot
shaft. Spark arrester bolt
9 Nm (0.9 m·kgf, 6.5 ft·lbf)
Muffler cap screw
5 Nm (0.5 m·kgf, 3.6 ft·lbf)
Pivot shaft
85 Nm (8.5 m·kgf, 61 ft·lbf)
New
New
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1
1
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Engine mounting bolt (lower side)
53 Nm (5.3 m·kgf, 38 ft·lbf)
Engine bracket bolt (front side)
34 Nm (3.4 m·kgf, 25 ft·lbf)
Engine mounting bolt (front side)
55 Nm (5.5 m·kgf, 40 ft·lbf)
Engine bracket bolt (upper side)
34 Nm (3.4 m·kgf, 25 ft·lbf)
Engine mounting bolt (upper
side)
45 Nm (4.5 m·kgf, 33 ft·lbf)
T R..
T R..
T R..
T R..
T R..
M
78
9
9 8
7
4 1
2
43
5
56

ENGINE REMOVAL
6-9
EAS2GB2236INSTALLING THE BRAKE PEDAL
1. Install:
• Spring “1”
• Brake pedal “2”
• O-rings “3”
• Bolt (brake pedal) “4”
•Clip “5”
TIP
Apply the lithium-soap-based grease on the
bolt, O-rings and brake pedal bracket.
EAS2GB2237INSTALLING THE DRIVE SPROCKET
1. Install:
• Drive sprocket “1”
• Drive chain “2”
TIP
Install the drive sprocket together with the drive
chain.
2. Install:
• Lock washer “1”
• Nut (drive sprocket) “2”
TIP
Tighten the nut while applying the rear brake.
ECA
NOTICE
Make sure to tighten to specification; other-
wise, it may damage the other part that is
fastened together.
3. Bend the lock washer tab to lock the nut.
4. Install:
• Drive sprocket guide
• Drive sprocket cover “1”
• Bolt (drive sprocket cover) “2”
EAS2GB2238INSTALLING THE EXHAUST PIPE AND
MUFFLER
1. Install:
•Gasket
• Exhaust pipe 1 “1”
• Nut (exhaust pipe 1) “2”
TIP
First temporarily tighten nuts to 13 Nm (1.3
m·kgf, 9.4 ft·lbf). Then retighten them to 20 Nm
(2.0 m·kgf, 14 ft·lbf). Bolt (brake pedal)
26 Nm (2.6 m·kgf, 19 ft·lbf)
Nut (drive sprocket)
75 Nm (7.5 m·kgf, 54 ft·lbf)
New
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1 2
3
45
LS
New
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Bolt (drive sprocket cover)
7 Nm (0.7 m·kgf, 5.1 ft·lbf)
Nut (exhaust pipe)
20 Nm (2.0 m·kgf, 14 ft·lbf)
T R..
21
New
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ENGINE REMOVAL
6-10
2. Install:
•Clamp
• Exhaust pipe 2 “1”
• Bolt (exhaust pipe 2) “2”
TIP
Install and temporarily tighten the exhaust pipe
2 with its end positioned as shown with respect
to the exhaust pipe 1.
3. Install:
•Clamp
• Silencer “1”
• Bolt (silencer) “2”
TIP
Install and temporarily tighten the silencer so
that its joint is positioned as shown with respect
to the exhaust pipe 2.
4. Tighten:
• Bolt (exhaust pipe 2)
•Clamp
TIP
Tighten while checking that their front and rear
joints are inserted in position.
Bolt (silencer)
30 Nm (3.0 m·kgf, 22 ft·lbf)
1
22
1
2
2mm (0.08in)
T R..
Bolt (exhaust pipe 2)
20 Nm (2.0 m·kgf, 14 ft·lbf)
Clamp
12 Nm (1.2 m·kgf, 8.7 ft·lbf)
1
22
2mm (0.08in)
T R..
T R..

CAMSHAFT
6-16
EAS2GB2244CHECKING THE DECOMPRESSION SYS-
TEM
1. Check:
• Decompression system
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Check that the decompressor cam “1”
moves smoothly.
b. Check that the decompressor lever pin “2”
projects from the camshaft.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS2GB2245INSTALLING THE CAMSHAFTS
1. Install:
• Exhaust camshaft “1”
• Intake camshaft “2”
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Turn the crankshaft counterclockwise with a
wrench.
TIP
• Apply molybdenum disulfide oil to the cam-
shafts.
• Apply the engine oil on the decompression
system.
b. Align the top dead center (TDC) mark “a” on
the rotor with the alignment mark “b” on the
crankcase cover.c. Fit the timing chain “3” onto both camshaft
sprockets and install the camshafts on the
cylinder head.
TIP
Make sure that the alignment mark “c” on the
exhaust camshaft sprocket and the alignment
mark “d” on the intake camshaft sprocket are
aligned with the edge of the cylinder head.
ECA
NOTICE
Do not turn the crankshaft during the cam-
shaft installation. Damage or improper
valve timing will result.
d. Install the clips, the camshaft caps and the
bolts (camshaft cap).
TIP
• Before installing the clips, cover the cylinder
head with a clean cloth to prevent the clips
from coming off into the cylinder head cavity.
• Tighten the bolts to the specified torque in two
or three steps in the proper tightening se-
quence as shown.
ECA
NOTICE
The bolts (camshaft cap) must be tightened
evenly, or damage to the cylinder head,
camshaft caps, and camshaft will result.
1
2
Bolt (camshaft cap)
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
ab
dc
3
T R..

CYLINDER HEAD
6-18
EAS2GB2246
CYLINDER HEAD
Removing the cylinder head
Order Part name Q’ty Remarks
Seat Refer to “GENERAL CHASSIS” on page 5-1.
Side cover (left/right) Refer to “GENERAL CHASSIS” on page 5-1.
Air scoop (left / right) Refer to “GENERAL CHASSIS” on page 5-1.
Fuel tank Refer to “FUEL TANK” on page 8-1.
Exhaust pipe and silencer Refer to “ENGINE REMOVAL” on page 6-1.
Radiator hose Disconnect.
Coolant temperature sensor coupler Disconnect.
Throttle body Refer to “THROTTLE BODY” on page 8-7.
Camshaft Refer to “CAMSHAFT” on page 6-11.
Upper engine bracket Refer to “ENGINE REMOVAL” on page 6-1.
1 Nut (cylinder head) 2
2 Bolt (cylinder head) 4
3 Cylinder head 1
4 Cylinder head gasket 1
5 Timing chain guide (intake side) 1
6 Oil check bolt 1
6
10 Nm (1.0 m kgf, 7.2 ft Ibf)T.R.
33 Nm (3.3 m kgf, 24 ft Ibf)T.R.
10 Nm (1.0 m kgf, 7.2 ft Ibf)T.R.

CYLINDER AND PISTON
6-33
EAS2GB2262CHECKING THE PISTON PIN
1. Check:
• Piston pin
Blue discoloration/grooves  Replace the
piston pin and then check the lubrication
system.
2. Measure:
• Piston pin outside diameter “a”
Out of specification  Replace the piston
pin.
3. Measure:
• Piston pin bore inside diameter “b”
Out of specification  Replace the piston.
EAS2GB2263INSTALLING THE PISTON AND CYLINDER
1. Install:
• Oil ring expander “1”
• Lower oil ring rail “2”
• Upper oil ring rail “3”
• Top ring “4”
TIP
Be sure to install the piston ring so that the
manufacturer’s marks or numbers face up.
2. Install:
• Piston “1”
• Piston pin “2”
• Piston pin clip “3”
TIP
• Apply the engine oil to the piston pin.
• Install the piston with the F mark “a” on it
pointing to its intake (front) side.
• Before installing the piston pin clip, cover the
crankcase opening with a cloth to prevent the
clip from falling into the crankcase.
• Install the piston pin clips, so that the clip ends
are 3 mm (0.12 in) “c” or more from the cutout
in the piston. Piston pin outside diameter
15.991–16.000 mm (0.6296–
0.6299 in)
Limit
15.971 mm (0.6288 in)
Piston pin bore inside diameter
16.002–16.013 mm (0.6300–
0.6304 in)
Limit
16.043 mm (0.6316 in)
b
4
New
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3
2 a

ELECTRIC STARTER
6-35
EAS2GB2264
ELECTRIC STARTER
Removing the starter motor
Order Job/Parts to remove Q’ty Remarks
Exhaust pipe Refer to “ENGINE REMOVAL” on page 6-1.
1 Starter motor 1
For assembly, reverse the disassemble pro-
cedure.
1
12 Nm (1.2 m kgf, 8.7 ft Ibf)T.R.

CLUTCH
6-40
EAS2GB2267
CLUTCH
Removing the clutch
Order Part name Q’ty Remarks
Engine oilDrain.
Refer to “CHANGING THE ENGINE OIL” on
page 3-17.
Brake pedal Refer to “ENGINE REMOVAL” on page 6-1.
1 Clutch cable 1 Disconnect.
2 Clutch cover 1
3Gasket 1
4 Clutch spring 5
5 Pressure plate 1
6 Push rod 1 1
7 Circlip 1
8Washer 1
9 Bearing 1
10 Ball 1
11 Push rod 2 1
12 Friction plate 1 4
13 Clutch plate 8
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2
3 45
(5)
(6)78961011
12
22
1
15
12
13
13
18
1920 17
16
14
13
T.R.
T.R.
T.R.
T.R.
LT
21

CLUTCH
6-42
Removing the right crankcase cover
Order Part name Q’ty Remarks
Engine guard Refer to “ENGINE REMOVAL” on page 6-1.
Engine oilDrain.
Refer to “CHANGING THE ENGINE OIL” on
page 3-17.
CoolantDrain.
Refer to “CHANGING THE COOLANT” on
page 3-10.
Brake pedal Refer to “ENGINE REMOVAL” on page 6-1.
Clutch cover Refer to “CLUTCH” on page 6-40.
1 Oil filter element cover 1
2 Oil filter element 1
3 Radiator pipe 2 1
4 Kickstarter lever 1
5 Right crankcase cover 1
6 Gaskets 1
7 Dowel pin 2
8Collar 1
For installation, reverse the removal proce-
dure.
T.R.
LS
New
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67
2
5
4
1
7 8
New
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LS
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LS

CLUTCH
6-45
EAS2GB2278CHECKING THE PRIMARY DRIVEN GEAR
1. Check:
• Primary driven gear
Damage/wear  Replace the primary drive
and primary driven gears as a set.
Excessive noise during operation  Re-
place the primary drive and primary driven
gears as a set.
EAS2GB2279INSTALLING THE OIL SEAL
1. Install:
• Oil seal “1”
• Washer “2”
• Circlip “3”
TIP
• Apply the lithium-soap-based grease on the
oil seal lip.
• Install the oil seal in parallel with its manufac-
ture's marks or numbers facing inward.
EAS2GB2280INSTALLING THE RIGHT CRANKCASE
COVER
1. Install:
• Dowel pin “1”
• O-ring “2”
• Collar “3”
• Gasket “4”
TIP
Apply the lithium-soap-based grease on the O-
ring.
2. Install:
• Right crankcase cover “1”• Right crankcase cover bolt “2”
TIP
• Apply the engine oil on the impeller shaft end.
• Mesh the impeller shaft gear “3” with primary
drive gear “4”.
• Tighten the right crankcase cover bolts in
stages and in a crisscross pattern.
EAS2GB2281INSTALLING THE CLUTCH
1. Install:
• Push lever shaft “1”
TIP
• Apply the lithium-soap-based grease on the
oil seal lip.
• Before installation, apply the engine oil to the
push lever shaft sliding surface.
New
New
3
2
1
LS
New
New
1
1
3
2
4
LS
Right crankcase cover bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
T R..
3
1
4
E
1
2