2014 YAMAHA YZ450F engine

CYLINDER HEAD
5-19
EAS1SL1214
CYLINDER HEAD
Removing the cylinder head
OrderPart nameQ’tyRemarks
SeatRefer 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 tankRefer to “FUEL TANK” on page 7-1.
Exhaust pipe and silencerRefer to “ENGINE REMOVAL” on page 5-1.
Radiator hoseDisconnect.
Coolant temperature sensor couplerDisconnect.
Throttle bodyRefer to “THROTTLE BODY” on page 7-5.
CamshaftRefer to “CAMSHAFT” on page 5-11.
Upper engine bracketRefer to “ENGINE REMOVAL” on page 5-1
1Bolt (cylinder head)2
2Bolt (cylinder head)4
3Cylinder head1
4Cylinder head gasket1
5Timing chain guide (intake side)1
6Oil check bolt2
7 66
1st
2nd
Final20 Nm (2.0 m
kgf, 14 ftIbf)T.
R.
30 Nm (3.0 mkgf, 22 ftIbf)
10 Nm (1.0 mkgf, 7.2 ftIbf)T.R.
10 Nm (1.0 mkgf, 7.2 ftIbf)T.R.
15 Nm (1.5 mkgf, 11 ftIbf)T.
R
.

CYLINDER AND PISTON
5-35
EAS1SL1230CHECKING 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.
EAS1SL1231INSTALLING THE PISTON AND CYLINDER
1. Install:
• Oil ring expander “1”
• Lower oil ring rail “2”
• Upper oil ring rail “3”
• 2nd ring “4”
• Top ring “5”
TIP
Be sure to install the piston rings 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.
Piston ring end gap
Top ring
End gap (installed)
0.20–0.30 mm (0.0079–0.0118 in)
Limit
0.55 mm (0.0217 in)
End gap (installed)
0.35–0.50 mm (0.0138–0.0197 in)
Limit
0.85 mm (0.0335 in)
Oil ring
End gap (installed)
0.20–0.50 mm (0.0079–0.0197 in)
Piston pin outside diameter
17.991–18.000 mm (0.7083–
0.7087 in)
Limit
17.971 mm (0.7075 in)
Piston pin bore inside diameter
18.004–18.015 mm (0.7088–
0.7093 in)
Limit
18.045 mm (0.7104 in)
b
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CLUTCH
5-37
EAS1SL1232
CLUTCH
Removing the clutch
OrderPart nameQ’tyRemarks
Engine oilDrain.Refer to “CHANGING THE ENGINE OIL” on page 3-15.
Brake pedalRefer to “ENGINE REMOVAL” on page 5-1.
1Clutch cable1Disconnect.
2Clutch cover1
3O-ring1
4Clutch spring6
5Pressure plate1
6Push rod 11
7Circlip1
8Washers1
9Bearing1
10Ball1
11Push rod 21
12Friction plate 15
13Clutch plate7
LS
LS
New
New
New
2
3 45
789
61011
13
12
12
18
1
14
13
13
17
16
15
T.R.
T.R.
T.R.
T.R.
LT

CLUTCH
5-39
Removing the right crankcase cover
OrderPart nameQ’tyRemarks
Right engine guardRefer to “ENGINE REMOVAL” on page 5-1.
Engine oilDrain.Refer to “CHANGING THE ENGINE OIL” on page 3-15.
CoolantDrain.Refer to “CHANGING THE COOLANT” on page 3-8.
Brake pedalRefer to “ENGINE REMOVAL” on page 5-1.
Clutch coverRefer to “CLUTCH” on page 5-37.
1Oil filter element cover1
2Oil filter element1
3Radiator pipe 21
4Kickstarter lever1
5Right crankcase cover1
6Gaskets1
7Dowel pin2
8Collar1
For installation, reverse the removal proce-dure.
T.R.
E
E
LS
New
New
67
2
5
4
1
7 8
New
3
LS
New
New
LS
NewNew
LT

CLUTCH
5-42
CHECKING 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.
EAS1SL1244INSTALLING THE OIL SEAL
1. Install:
• Oil seal “1”
• Washer “2”
• Circlip “3”
TIP
• Apply is 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.
EAS1SL1245INSTALLING THE RIGHT CRANKCASE
COVER
1. Install:
• Dowel pin “1”
• O-rings “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.
• When installing the crankcase cover onto the
crankcase, make sure that the impeller shaft
end “3” aligns with the balancer end slot “4.”
• Tighten the right crankcase cover bolts in
stages and in a crisscross pattern.
EAS1SL1246INSTALLING THE CLUTCH
1. Install:
• Push lever shaft “1”
TIP
• Apply the lithium soap base 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 4
2
New
New
3
LS
Right crankcase cover bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)T R..
12
1

CLUTCH
5-43
2. Install:
• Primary driven gear “1”
• Thrust washer “2”
• Clutch boss “3”
TIP
Apply the engine oil on the primary driven gear
inner circumference.
3. Install:
• Conical washer “1”
• Clutch boss nut “2”
ECA1DX1020
NOTICE
Make sure to tighten to specification; other-
wise, it may damage the other part that is
fastened together.
TIP
• Install the conical washer with its convex sur-
face “a” outward.
• Apply engine oil to the threads and contact
surface of the clutch boss nut.
• Apply engine oil to the contact surfaces of the
conical washer.
• Use the clutch holding tool “3” to hold the
clutch boss.
4. Install:
• Friction plate 1 “1”
• Clutch plate “2”
• Friction plate 2 “3”
TIP
• Install the clutch plates and friction plates al-
ternately on the clutch boss, starting with a
friction plate and ending with a friction plate.
• From the clutch boss side, install the friction
plates in order: friction plate 1  3, friction
plate 2 (identification color: purple)  3, and
friction plate 1  2.
• Apply the engine oil on the friction plates and
clutch plates.
5. Install:
• Bearing “1”
• Washer “2”
• Circlip “3”
To push rod 1 “4.”
TIP
Apply the engine oil on the bearing and washer.
Clutch boss nut
75 Nm (7.5 m·kgf, 54 ft·lbf)
Clutch holder
90890-04086
YM-91042
New
T R..
a2
3
21
a. Identification color
1
2a
3
2
2
1
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CLUTCH
5-44
6. Install:
• Push rod 2 “1”
•Ball “2”
• Push rod 1 “3”
TIP
Apply the engine oil on the push rod 1, 2 and
ball.
7. Install:
• Pressure plate “1”
8. Install:
• Clutch spring
• Clutch spring bolt
TIP
Tighten the bolts in stages and in a crisscross
pattern.
9. Install:
• O-ring “1”
TIP
Apply the lithium-soap-based grease to the O-
ring.
10.Install:
• Clutch cover “1”
• Clutch cover bolt
TIP
Tighten the bolts in stages and in a crisscross
pattern.
EAS1SL1247
Clutch spring bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)T R..
Clutch cover bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
New
T R..
1

KICKSTATER
5-48
3. Install:
• Spring guide “1”
TIP
Slide the spring guide into the kick shaft, make
sure the groove “a” in the spring guide fits on
the stopper of the torsion spring.
4. Install:
• Kick shaft assembly “1”
TIP
• Before installation, apply molybdenum disul-
fide grease to the contacting surfaces of the
kick shaft ratchet wheel guide “2” and the kick
shaft stopper “a.”
• Apply the engine oil on the kick shaft.
• Slide the kick shaft assembly into the crank-
case and make sure the kick shaft stopper “a”
fits into the kick shaft ratchet wheel guide.
5. Install:
• Torsion spring “1”
TIP
Turn the torsion spring clockwise and hook into
the proper hole “a” in the crankcase.
EAS1SL1253INSTALLING THE KICK IDLE GEAR
1. Install:
• Kick idle gear “1”
• Washer “2”
• Circlip “3”
TIP
• Apply the engine oil on the kick idle gear inner
circumference.
• Install the kick idle gear with its depressed
side “a” toward you.
1 2a b
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