2015 YAMAHA WR 250F engine

6
ENGINE
ENGINE REMOVAL......................................................................................... 6-1
REMOVING THE SILENCER ..................................................................... 6-6
REMOVING THE EXHAUST PIPE 2.......................................................... 6-6
REMOVING THE DRIVE SPROCKET ....................................................... 6-6
REMOVING THE ENGINE ......................................................................... 6-7
CLEANING THE SPARK ARRESTER ....................................................... 6-7
CHECKING THE SILENCER AND EXHAUST PIPE.................................. 6-8
INSTALLING THE ENGINE........................................................................ 6-8
INSTALLING THE BRAKE PEDAL ............................................................ 6-9
INSTALLING THE DRIVE SPROCKET...................................................... 6-9
INSTALLING THE EXHAUST PIPE AND MUFFLER................................. 6-9
CAMSHAFT.................................................................................................... 6-11
REMOVING THE CAMSHAFT ................................................................. 6-13
CHECKING THE CAMSHAFT.................................................................. 6-14
CHECKING THE TIMING CHAIN AND CAMSHAFT SPROCKET .......... 6-15
CHECKING THE TIMING CHAIN TENSIONERS .................................... 6-15
CHECKING THE DECOMPRESSION SYSTEM...................................... 6-16
INSTALLING THE CAMSHAFTS ............................................................. 6-16
CYLINDER HEAD........................................................................................... 6-18
REMOVING THE CYLINDER HEAD........................................................ 6-20
CHECKING THE TIMING CHAIN GUIDE (INTAKE SIDE) ...................... 6-20
CHECKING THE CYLINDER HEAD ........................................................ 6-20
INSTALLING THE CYLINDER HEAD ...................................................... 6-21
VALVES AND VALVE SPRINGS................................................................... 6-22
REMOVING THE VALVES ....................................................................... 6-23
CHECKING THE VALVES AND VALVE GUIDES ................................... 6-24
CHECKING THE VALVE SEATS ............................................................. 6-26
CHECKING THE VALVE SPRINGS......................................................... 6-27
CHECKING THE VALVE LIFTERS .......................................................... 6-28
INSTALLING THE VALVES ..................................................................... 6-28
CYLINDER AND PISTON............................................................................... 6-30
REMOVING THE PISTON ....................................................................... 6-31
CHECKING THE CYLINDER AND PISTON ............................................ 6-31
CHECKING THE PISTON RINGS............................................................ 6-32
CHECKING THE PISTON PIN ................................................................. 6-33
INSTALLING THE PISTON AND CYLINDER .......................................... 6-33
ELECTRIC STARTER.................................................................................... 6-35
CHECKING THE STARTER MOTOR ...................................................... 6-37
ASSEMBLING THE STARTER MOTOR .................................................. 6-38

ENGINE REMOVAL
6-1
EAS2GB2227
TIP
This section is intended for those who have basic knowledge and skill concerning the servicing of
Yamaha motorcycles (e.g., Yamaha dealers, service engineers, etc.). Those who have little knowl-
edge and skill concerning servicing are requested not to undertake inspection, adjustment, disas-
sembly, or reassembly only by reference to this manual. It may lead to servicing trouble and
mechanical damage.
EAS2GB2228
ENGINE REMOVAL
Removing the exhaust pipe
Order Part name Q’ty Remarks
Side cover (right) Refer to “GENERAL CHASSIS” on page 5-1.
Rear shock absorber assembly lower boltRefer to “REAR SHOCK ABSORBER AS-
SEMBLY” on page 5-57.
Connecting arm bolt (frame side)Refer to “REAR SHOCK ABSORBER AS-
SEMBLY” on page 5-57.
1 Silencer clamp 1 Loosen.
2 Silencer 1
3 Exhaust pipe 2 clamp 1 Loosen.
4 Exhaust pipe 2 1
5 Exhaust pipe 1 1
105 9
26
1
66
3
84 7 (4) (6)
30 Nm (3.0 m kgf, 22 ft Ibf)T.R.
30 Nm (3.0 m kgf, 22 ft Ibf)T.R.
9 Nm (0.9 m kgf, 6.5 ft Ibf)T.R.
10 Nm (1.0 m kgf, 7.2 ft Ibf)T.R.
New
New
10 Nm (1.0 m kgf, 7.2 ft Ibf)T.R.
12 Nm (1.2 m kgf, 8.7 ft Ibf)T.R.12 Nm (1.2 m kgf, 8.7 ft Ibf)T.R.
20 Nm (2.0 m kgf, 14 ft Ibf)T.R.New
1st
2nd 20 Nm (2.0 m kgfkgf
, 14 ft lbf) 13 Nm (1.3 m , 9.4 ft lbf)T.R.
LT
LT
5 Nm (0.5 m kgf, 3.6 ft Ibf)T.R.

ENGINE REMOVAL
6-2
6 Gaskets 3
7 Exhaust pipe 1 protector 1
8 Exhaust pipe 2 protector 1
9 Silencer cap 1
10 Spark arrester 1
For installation, reverse the removal proce-
dure.
Removing the exhaust pipe
Order Part name Q’ty Remarks
105 9
26
1
66
3
84 7 (4) (6)
30 Nm (3.0 m kgf, 22 ft Ibf)T.R.
30 Nm (3.0 m kgf, 22 ft Ibf)T.R.
9 Nm (0.9 m kgf, 6.5 ft Ibf)T.R.
10 Nm (1.0 m kgf, 7.2 ft Ibf)T.R.
New
New
10 Nm (1.0 m kgf, 7.2 ft Ibf)T.R.
12 Nm (1.2 m kgf, 8.7 ft Ibf)T.R.12 Nm (1.2 m kgf, 8.7 ft Ibf)T.R.
20 Nm (2.0 m kgf, 14 ft Ibf)T.R.New
1st
2nd 20 Nm (2.0 m kgfkgf
, 14 ft lbf) 13 Nm (1.3 m , 9.4 ft lbf)T.R.
LT
LT
5 Nm (0.5 m kgf, 3.6 ft Ibf)T.R.

ENGINE REMOVAL
6-3
Removing the electronic parts
Order Part name Q’ty Remarks
Use a suitable stand to raise the front wheel
off the ground.
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.
Air filter case cover
1 Rectifier/regulator 1
2ECU 1
3 Ignition coil 1
4 Neutral switch 1
5 AC magneto coupler 1 Disconnect.
6 Crankshaft position sensor coupler 1 Disconnect.
7 Coolant temperature sensor coupler 1 Disconnect.
For installation, reverse the removal proce-
dure.
T.R.
T.R.
T.R.T.R.
7 3
6
5
142
LT
New
LS

ENGINE REMOVAL
6-4
Removing the engine
Order Part name Q’ty Remarks
Use a suitable stand to raise the front wheel
off the ground.
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.
Air filter case Refer to “THROTTLE BODY” on page 8-7.
Throttle body Refer to “THROTTLE BODY” on page 8-7.
Clutch cable Refer to “CLUTCH” on page 6-40.
Shift pedal Refer to “SHIFT SHAFT” on page 6-52.
Starter motor 1Refer to “ELECTRIC STARTER” on page 6-
35.
1 Engine guard 1
2 Brake pedal 1
3Spring 1
New
New
LS
M
8
8
7
6
13
45
New
1 12
3
2
1110
9
55 Nm (5.5 m kgf, 40 ft Ibf)T.R.

ENGINE REMOVAL
6-5
4 Cylinder head breather hose 1
5 Drive sprocket cover 1
6 Drive chain guide 1
7 Drive sprocket 1
8 Upper engine bracket 2
9 Washer 1 Thickness:2.3 mm (0.09 in)
10 Washer 1 Thickness:1.0 mm (0.04 in)
11 Lower engine bracket 2
12 Pivot shaft 1
13 Engine 1
For installation, reverse the removal proce-
dure.
Removing the engine
Order Part name Q’ty Remarks
New
New
LS
M
8
8
7
6
13
45
New
1 12
3
2
1110
9
55 Nm (5.5 m kgf, 40 ft Ibf)T.R.

ENGINE REMOVAL
6-6
EAS2GB2229REMOVING THE SILENCER
1. Remove:
• Rear shock absorber assembly lower bolt
“1”
• Connecting arm bolt (frame side) “2”
• Silencer “3”
TIP
Move the rear shock absorber to the left side of
the chassis, and remove the silencer.
EAS2GB2230REMOVING THE EXHAUST PIPE 2
1. Remove:
• Exhaust pipe 2
TIP
Put the Exhaust pipe 2 into the state as shown
by moving this, and then remove it.
EAS2GB2231REMOVING THE DRIVE SPROCKET
1. Straighten the lock washer tab.
2. Remove:
• Nut (drive sprocket) “1”
• Lock washer “2”
TIP
Loosen the nut while applying the rear brake.
3. Remove:
• Drive sprocket “1”
• Drive chain “2”
TIP
Remove the drive sprocket together with the
drive chain.
1 2
3

ENGINE REMOVAL
6-7
EAS2GB2232REMOVING THE ENGINE
1. Remove:
• Pivot shaft “1”
TIP
If the pivot shaft is pulled all the way out, the
swingarm will come loose. If possible, insert a
shaft of similar diameter into the other side of
the swingarm to support it.
2. Remove:
• Engine “1”
From the right side.
TIP
• Make sure that the couplers, the hoses, and
the cables are disconnected.
• Lift up the engine, and remove this from its
lower part toward the right of the chassis.
EAS2GB2233
CLEANING THE SPARK ARRESTEREWA
WARNING
• Be sure the exhaust pipe and muffler are
cool before cleaning the spark arrester.
• Do not start the engine when cleaning the
exhaust system.
1. Remove:
• Muffler cap screws “1”
2. Remove:
• Spark arrester bolts “1”
3. Remove:
• Tail pipe “1”
• Tail pipe gasket “2”
• Spark arrester “3”
Pull the spark arrester out of the muffler.
• Spark arrester gasket “4”
4. Clean:
• Spark arrester
Tap the spark arrester lightly, then use a
wire brush to remove any carbon deposits.
1