engine YAMAHA YZ250F 2016 Repair Manual

ENGINE REMOVAL
5-2
5 Exhaust pipe 1 1
6 Gaskets 3
7 Exhaust pipe 1 protector 1
8 Exhaust pipe 2 protector 1
9 Silencer body 1
10 Silencer cap 1
For installation, reverse the removal proce-
dure.
Removing the exhaust pipe
Order Part name Q’ty Remarks
10
5
9
2 6
1
66
3
84 7 (8)
(6)
30 Nm (3.0 m kgf, 22 ft Ibf)T.R.
30 Nm (3.0 m kgf, 22 ft Ibf)T.R.
8 Nm (0.8 m kgf, 5.8 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
20 Nm (2.0 m kgf, 14 ft lbf) 13 Nm (1.3 m kgf, 9.4 ft lbf)T.R.
LT
LT
LT
*

ENGINE REMOVAL
5-3
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 4-1.
Side cover (left/right) Refer to “GENERAL CHASSIS” on page 4-1.
Air scoop (left / right) Refer to “GENERAL CHASSIS” on page 4-1.
Fuel tank Refer to “FUEL TANK” on page 7-1.
Air filter case cover
1 Rectifier/regulator 1
2ECU 1
3 Ignition coil 1
4 Condenser 1
5 Neutral switch 1
6 AC magneto coupler 1 Disconnect.
7 Crankshaft position sensor coupler 1 Disconnect.
8 Coolant temperature sensor coupler 1 Disconnect.
For installation, reverse the removal proce-
dure.
T.R.
T.R.
T.R.T.R.
8 3
7
6
154
2
LT
New
LS

ENGINE REMOVAL
5-4
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 4-1.
Side cover (left/right) Refer to “GENERAL CHASSIS” on page 4-1.
Air scoop (left / right) Refer to “GENERAL CHASSIS” on page 4-1.
Fuel tank Refer to “FUEL TANK” on page 7-1.
Exhaust pipe and silencer Refer to “ENGINE REMOVAL” on page 5-1.
Air filter case Refer to “THROTTLE BODY” on page 7-5.
Throttle body Refer to “THROTTLE BODY” on page 7-5.
Clutch cable Refer to “CLUTCH” on page 5-35.
Shift pedal Refer to “SHIFT SHAFT” on page 5-47.
1 Engine guard 1
2 Brake pedal 1
3Spring 1
4 Cylinder head breather hose 1
5 Drive sprocket cover 1
New
New
LS
M
8
8
7
6
13
45
New
1 12
3
2
1110 9
55 Nm (5.5 mkgf, 40 ftIbf)T.R.

ENGINE REMOVAL
5-5
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 mkgf, 40 ftIbf)T.R.

ENGINE REMOVAL
5-6
EAS1SM9195REMOVING 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.
EAS1SM9196REMOVING 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.
EAS1SM9197REMOVING 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
5-7
EAS1SM9198REMOVING 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.
EAS1SM9199CHECKING THE SILENCER AND EXHAUST
PIPE
1. Check:
•Gasket “1”
Damage  Replace.
EAS1SM9200CHANGING THE SILENCER FIBER
1. Remove:
•Bolt “1”
• Silencer body “2”
ECANOTICE
Do not hit the silencer stay “a” as it may do
damage to the silencer.
TIP
Remove the inner pipe while holding the silenc-
er in place with a vise etc.
2. Remove:
•Rivet “1”
• Silencer cap “2”
1
1
1
a
1
2
2
1

ENGINE REMOVAL
5-8
3. Replace:
• Fiber “1”
4. Install:
• Silencer body “1”
•Bolt “2”
TIP
Apply heat-resistant sealant to the areas “a”
shown, making sure that there are no gaps in
the beads of sealant.
5. Replace:
• Fiber “1”
TIP
Stuff the fiber into the silencer body by using a
flat board “2”.
6. Install:
• Silencer cap “1”
•Rivet “2”
TIP
• Apply heat-resistant sealant to the areas “a”
shown, making sure that there are no gaps in
the beads of sealant.
• Take care not to allow the fiber out of place
when installing the silencer body “3”.
EAS1SM9201INSTALLING 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. Silencer body bolt
8 Nm (0.8 m·kgf, 5.8 ft·lbf)
LOCTITE®
1
T R..
a
12LT
2
1
Pivot shaft
85 Nm (8.5 m·kgf, 61 ft·lbf)
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)
1
1 a233
T R..
T R..
T R..
T R..
T R..
T R..

ENGINE REMOVAL
5-9
EAS1SM9202INSTALLING 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.
EAS1SM9203INSTALLING 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” Bolt (brake pedal)
26 Nm (2.6 m·kgf, 19 ft·lbf)
M
78
9
9 8
7
4 1
2
43
5
56
New
T R..
1 2
3
45
LS
Nut (drive sprocket)
75 Nm (7.5 m·kgf, 54 ft·lbf)
Bolt (drive sprocket cover)
7 Nm (0.7 m·kgf, 5.1 ft·lbf)
New
T R..
T R..
21

ENGINE REMOVAL
5-10
EAS1SM9204INSTALLING THE EXHAUST PIPE AND
MUFFLER
1. Install:
•Gasket
• Exhaust pipe 1 “1”
• Nut (exhaust pipe 1) “2”
TIP
First temporarily tighten all 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).
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. Nut (exhaust pipe)
20 Nm (2.0 m·kgf, 14 ft·lbf)
New
T R..
1
22
1
2
2mm (0.08in)
Bolt (silencer)
30 Nm (3.0 m·kgf, 22 ft·lbf)
Bolt (exhaust pipe 2)
20 Nm (2.0 m·kgf, 14 ft·lbf)
Clamp
12 Nm (1.2 m·kgf, 8.7 ft·lbf)
T R..
2
2
1
2mm (0.08in)
T R..
T R..

CAMSHAFT
5-16
EAS1SM9210CHECKING 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.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS1SM9211INSTALLING 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.
ECA33DD029NOTICE
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.
• Apply the engine oil to the threads and con-
tact surfaces.
• Tighten the bolts to the specified torque in two
or three steps in the proper tightening se-
quence as shown.
ECA33DD030NOTICE
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)
b
a
dc
3
T R..