2010 YAMAHA YZ450F Owners Manual

4-48
ENGINE REMOVAL
REMOVING THE ENGINE
Order Part name Q'ty Remarks
Hold the machine by placing the suitable stand
under the frame.Refer to "HANDLING NOTE".
Throttle body Refer to "THROTTLE BODY" section in the
CHAPRE 6.
Rear fenderRefer to "SEAT AND SIDE COVERS" sec-
tion.
Exhaust pipe and silencer Refer to "EXHAUST PIPE AND SILENCER"
section.
Clutch cable Disconnect at the engine side.
Shift pedalRefer to "KICK SHAFT AND SHIFT SHAFT"
section.
Cylinder head breather hose Refer to "CAMSHAFTS" section.
Drain the engine oil.Refer to "CHANGING THE ENGINE OIL"
section in the CHAPTER 3.
Engine guard (Right)
1 Drive chain sprocket cover 1
2 Nut (drive sprocket) 1 Refer to removal section.
3 Lock washer 1 Refer to removal section.
4 Drive sprocket 1 Refer to removal section.

4-49
ENGINE REMOVAL
5Clip 1
6 Bolt (brake pedal) 1
7 Brake pedal 1
8 Upper engine bracket 2
9 Lower engine bracket 2
10 Engine mounting bolt 4
11 Pivot shaft 1 Refer to removal section.
12 Engine 1 Refer to removal section. Order Part name Q'ty Remarks

4-50
ENGINE REMOVAL
HANDLING NOTE
Support the machine securely so
there is no danger of it falling over.
REMOVING THE DRIVE
SPROCKET
1. Remove:
• Nut (drive sprocket) "1"
• Lock washer "2"
• Straighten the lock washer tab.
• Loosen the nut while applying the
rear brake.
2. Remove:
• Drive sprocket "1"
• Drive chain "2"
Remove the drive sprocket together
with the drive chain.
REMOVING THE ENGINE
1. Remove:
• Pivot shaft "1"
If the pivot shaft is pulled all the way
out, the swingarm will come loose. If
possible, insert a shaft of similar di-
ameter into the other side of the swin-
garm to support it.
2. Remove:
• Engine "1"
From right side.
• Make sure that the couplers, hoses
and cables are disconnected.
• Turn the engine 90° to the right as
shown, and then, while lifting the
crankcase in the direction of the ar-
row shown, remove the engine from
the right side of the vehicle.
INSTALLING THE ENGINE
1. Install:
• Engine "1"
Install the engine from right side.
• Pivot shaft "2"
• Engine mounting bolt (lower) "3"
• Lower engine bracket "4"
• Bolt (lower engine bracket) "5"
• Patch "6"
• Engine mounting bolt (front) "7"
• Upper engine bracket "8"
• Bolt (upper engine bracket) "9"
• Engine mounting bolt (upper) "10"
• Apply the molybdenum disulfide
grease on the pivot shaft.
• Install the patch with the claw "6"
facing outside the chassis.
INSTALLING THE BRAKE PEDAL
1. Install:
• Spring "1"
• Brake pedal "2"
• O-ring "3"
• Bolt (brake pedal) "4"
• Clip "5"
Apply the lithium soap base grease
on the bolt, O-rings and brake pedal
bracket.
INSTALLING THE DRIVE
SPROCKET
1. Install:
• Drive sprocket "1"
• Drive chain "2"
Install the drive sprocket together
with the drive chain.
Pivot shaft:
85 Nm (8.5 m•kg, 61
ft•lb)
Engine mounting bolt
(lower):
53Nm (5.3 m•kg, 38
ft•lb)
Bolt (lower engine brack-
et):
34 Nm (3.4 m•kg, 24
ft•lb)
Engine mounting bolt
(front):
53 Nm (5.3 m•kg, 38
ft•lb)
Bolt (upper engine brack-
et):
45 Nm (4.5 m•kg, 32
ft•lb)
Engine mounting bolt
(upper):
45 Nm (4.5 m•kg, 32
ft•lb)
Bolt (brake pedal):
26 Nm (2.6 m•kg, 19
ft•lb)

4-51
ENGINE REMOVAL
2. Install:
• Lock washer "1"
• Nut (drive sprocket) "2"
Tighten the nut while applying the
rear brake.
Make sure to tighten to specifica-
tion; otherwise, it may damage the
other part that is fastened togeth-
er.
3. Bend the lock washer tab to lock
the nut.
4. Install:
• Drive chain sprocket guide
• Drive chain sprocket cover "1"
• Bolt(drive chain sprocket cover)
"2"Nut (drive sprocket):
75 Nm (7.5 m•kg, 54
ft•lb)
Bolt (drive chain sprock-
et cover):
7 Nm (0.7 m•kg, 5.1
ft•lb)

4-52
CRANKCASE AND CRANKSHAFT
CRANKCASE AND CRANKSHAFT
REMOVING THE CRANKSHAFT
Order Part name Q'ty Remarks
Engine Refer to "ENGINE REMOVAL" section.
Piston Refer to "CYLINDER AND PISTON" section.
Balancer Refer to "BALANCER" section.
Kick shaft assemblyRefer to "KICK SHAFT AND SHIFT SHAFT"
section.
SegmentRefer to "KICK SHAFT AND SHIFT SHAFT"
section.
Stator Refer to "AC MAGNETO" section.
1 Timing chain guide (exhaust side) 1
2 Timing chain guide stopper plate 1
3 Timing chain 1
4 Bolt [L = 50 mm (1.97 in)] 7 Refer to removal section.
5 Bolt [L = 60 mm (2.36 in)] 2 Refer to removal section.
6 Bolt [L = 70 mm (2.76 in)] 4 Refer to removal section.
7 Right crankcase 1 Refer to removal section.
8 Left crankcase 1 Refer to removal section.
9 Oil strainer 1

4-53
CRANKCASE AND CRANKSHAFT
10 Balancer shaft 1 Refer to removal section.
11 Crankshaft 1 Refer to removal section. Order Part name Q'ty Remarks

4-54
CRANKCASE AND CRANKSHAFT
REMOVING THE CRANKCASE BEARING
Order Part name Q'ty Remarks
TransmissionRefer to "TRANSMISSION, SHIFT CAM AND
SHIFT FORK" section.
Shift cam and shift fork Refer to "TRANSMISSION, SHIFT CAM AND
SHIFT FORK" section.
1 Circlip 1
2 Oil seal 3
3 Bearing 10 Refer to removal section.

4-55
CRANKCASE AND CRANKSHAFT
DISASSEMBLING THE
CRANKCASE
1. Separate:
• Right crankcase
• Left crankcase
Separation steps:
a. Remove the crankcase bolts,
hose guide and clutch cable hold-
er.
Loosen each bolt 1/4 of a turn at a
time and after all the bolts are loos-
ened, remove them.
b. Remove the right crankcase "1".
• Place the crankcase with its left
side downward and split it by insert-
ing a screwdriver tip into the split-
ting slit "a" in the crankcase.
• Lift the right crankcase horizontally
while lightly patting the case split-
ting slit and engine mounting boss
using a soft hammer, and leave the
crankshaft and transmission with
the left crankcase.
Use soft hammer to tap on the
case half. Tap only on reinforced
portions of case. Do not tap on
gasket mating surface. Work slow-
ly and carefully. Make sure the
case halves separate evenly. If the
cases do not separate, check for a
remaining case bolt or fitting. Do
not force.
c. Remove the dowel pins and O-
ring.
REMOVING THE BALANCER
SHAFT
1. Remove:
• Balancer shaft "1"
Remove the balancer shaft with its
flat side "a" facing the crankshaft.
REMOVING THE CRANKSHAFT
1. Remove:
• Crankshaft "1"
Use the crankcase separating
tool "2".
• Install the crankcase separating
tool as shown.
• Do not use a hammer to drive out
the crankshaft.
REMOVING THE CRANKCASE
BEARING
1. Remove:
• Bearing "1"
• Remove the bearing from the
crankcase by pressing its inner
race.
• Do not use the removed bearing.
CHECKING THE TIMING CHAIN
AND TIMING CHAIN GUIDE
1. Inspect:
• Timing chain
Cracks/stiff→Replace the timing
chain and camshaft sprocket as a
set.
2. Inspect:
• Timing chain guide
Wear/damage→Replace.
CHECKING THE CRANKCASE
1. Inspect:
• Contacting surface "a"
Scratches → Replace.
• Engine mounting boss "b", crank-
case
Cracks/damage → Replace.
2. Inspect:
• Bearing
Rotate inner race with a finger.
Rough spot/seizure → Replace.
Crankcase separating
tool:
YU-A9642/90890-04152