fuel YAMAHA YZ450F 2009 Owner's Manual

4-2
SEAT, FUEL TANK AND SIDE COVERS
REMOVING THE SIDE COVER
1. Remove:
• Bolt (side cover)
• Left side cover "1"
• Right side cover "2"
Draw the side cover downward to re-
move it because its claws "a" are in-
serted in the air filter case.
REMOVING THE NUMBER PLATE
1. Remove:
• Bolt (number plate)
• Number plate "1"
• The projection "a" is inserted into
the band of the number plate. Pull
the band off the projection before
removal.
• Remove the hot starter cable "2"
and clutch cable "3" from the cable
guide "b" on the number plate.
• The projection "c" on the lower
bracket is inserted into the number
plate. Remove the number plate by
pulling it off the projection.
INSTALLING THE AIR SCOOP
1. Install
• Air scoop "1"
• Bolt (air scoop)
Put the portion "a" of the flap of the air
filter case on the inside of the air
scoop.
Bolt (air scoop):
7 Nm (0.7 m•kg, 5.1
ft•lb)

4-3
EXHAUST PIPE AND SILENCER
EXHAUST PIPE AND SILENCER
REMOVING THE EXHAUST PIPE AND SILENCER
Order Part name Q'ty Remarks
Right side coverRefer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
1 Bolt (silencer clamp) 1 Only loosening.
2 Bolt [silencer (front)] 1
3 Bolt [silencer (rear)] 1
4Collar 1
5 Silencer 1
6 Silencer clamp 1
7 Nut (exhaust pipe) 1
8 Bolt (exhaust pipe) 1
9 Exhaust pipe 1
10 Gasket 2

4-5
RADIATOR
RADIATOR
REMOVING THE RADIATOR
Order Part name Q'ty Remarks
Drain the coolant.Refer to "CHANGING THE COOLANT" sec-
tion in the CHAPTER 3.
Seat and fuel tankRefer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
Exhaust pipeRefer to "EXHAUST PIPE AND SILENCER"
section.
1 Radiator guard 2
2 Radiator hose clamp 8 Only loosening.
3 Right radiator 1
4 Radiator hose 2 1
5 Radiator hose 3 1
6 Radiator hose 4 1
7 Pipe 2/O-ring 1/1
8 Radiator breather hose 1
9 Left radiator 1
10 Radiator hose 1 1
11 Pipe 1/O-ring 1/1

4-7
CARBURETOR
CARBURETOR
REMOVING THE CARBURETOR
Order Part name Q'ty Remarks
Seat and fuel tank Refer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
Rear shock absorber Refer to "REAR SHOCK ABSORBER" sec-
tion in the CHAPTER 5.
1Clamp 1
2 Throttle position sensor lead coupler 1
3 Throttle cable cover 1
4 Throttle cable 2
5 Clamp (air filter joint) 1 Loosen the screw (air filter joint).
6 Clamp (carburetor joint) 1 Loosen the screws (carburetor joint).
7 Hot starter plunger 1
8 Carburetor assembly 1
9 Carburetor joint 1

4-10
CARBURETOR
HANDLING NOTE
Do not loosen the screw (throttle
position sensor) "1" except when
changing the throttle position sen-
sor due to failure because it will
cause a drop in engine perfor-
mance.
REMOVING THE PILOT SCREW
1. Remove:
• Pilot screw "1"
To optimize the fuel flow at a small
throttle opening, each machine's pilot
screw has been individually set at the
factory. Before removing the pilot
screw, turn it in fully and count the
number of turns. Record this number
as the factory-set number of turns
out.
CHECKING THE CARBURETOR
1. Inspect:
• Carburetor body
Contamination→Clean.
• Use a petroleum based solvent for
cleaning. Blow out all passages and
jets with compressed air.
• Never use a wire.
2. Inspect:
•Main jet "1"
• Pilot jet "2"
• Needle jet "3"
• Starter jet "4"
• Pilot air jet "5"•Leak jet "6"
Damage→Replace.
Contamination→Clean.
• Use a petroleum based solvent for
cleaning. Blow out all passages and
jets with compressed air.
• Never use a wire.
CHECKING THE NEEDLE VALVE
1. Inspect:
• Needle valve "1"
• Valve seat "2"
Grooved wear "a" →Replace.
Dust "b" →Clean.
•Filter "c"
Clogged→Clean.
CHECKING THE THROTTLE
VALVE
1. Check:
• Free movement
Stick→Repair or replace.
Insert the throttle valve "1" into the
carburetor body, and check for free
movement.
CHECKING THE JET NEEDLE
1. Inspect:
• Jet needle "1"
Bends/wear→Replace.
• Clip groove
Free play exists/wear→Replace.
• Clip positionMEASURING AND ADJUSTING
THE FLOAT HEIGHT
1. Measure:
• Float height "a"
Out of specification→Adjust.
Measurement and adjustment
steps:
a. Hold the carburetor in an upside
down position.
• Slowly tilt the carburetor in the op-
posite direction, then take the mea-
surement when the needle valve
aligns with the float arm.
• If the carburetor is level, the weight
of the float will push in the needle
valve, resulting in an incorrect mea-
surement.
b. Measure the distance between
the mating surface of the float
chamber and top of the float using
a vernier calipers.
The float arm should be resting on the
needle valve, but not compressing
the needle valve.
c. If the float height is not within
specification, inspect the valve
seat and needle valve.
d. If either is worn, replace them
both.
e. If both are fine, adjust the float
height by bending the float tab "b"
on the float.
Standard clip position:
No.3 Groove
Float height:
8.0 mm (0.31 in)

4-14
CAMSHAFTS
CAMSHAFTS
REMOVING THE CYLINDER HEAD COVER
Order Part name Q'ty Remarks
Seat and fuel tank Refer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
Hot starter plunger Refer to "CARBURETOR" section.
Engine upper bracket (right) Refer to "ENGINE REMOVAL" section.
Engine upper bracket (left)
1 Spark plug 1
2 Cylinder head breather hose 1
3 Bolt (cylinder head cover) 2
4 Cylinder head cover 1
5 Cylinder head cover gasket 1
6 Timing chain guide (top side) 1

4-19
CYLINDER HEAD
CYLINDER HEAD
REMOVING THE CYLINDER HEAD
Tighten the cylinder head bolts to 30 Nm (3.0 m•kg, 22 ft•lb) in the proper tightening sequence, remove and retighten the
cylinder head bolts to 20 Nm (2.0 m•kg, 14 ft•lb) in the proper tightening sequence, and then tighten the cylinder head bolts
further to reach the specified angle 180° in the proper tightening sequence.
Order Part name Q'ty Remarks
Seat and fuel tank Refer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
Exhaust pipe and silencerRefer to "EXHAUST PIPE AND SILENCER"
section.
Radiator Refer to "RADIATOR" section
Carburetor Refer to "CARBURETOR" section.
Camshaft Refer to "CAMSHAFTS" section.
1Bolt 2
2* Bolt 4 Refer to NOTE.
3 Cylinder head 1
4Gasket 1
5 Timing chain guard (exhaust side) 1

4-47
CDI MAGNETO
CDI MAGNETO
REMOVING THE CDI MAGNETO
Order Part name Q'ty Remarks
Seat and fuel tank Refer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
Disconnect the CDI magneto lead.
1 Left crankcase cover 1
2Gasket 1
3 Dowel pin 2
4 Nut (rotor) 1 Refer to removal section.
5 Rotor 1 Refer to removal section.
6 Stator 1
7 Woodruff key 1

4-49
ENGINE REMOVAL
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".
Seat and fuel tank Refer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
Rear shock absorber Refer to "REAR SHOCK ABSORBER" sec-
tion in the CHAPTER 5.
Carburetor Refer to "CARBURETOR" section.
Exhaust pipe and silencer Refer to "EXHAUST PIPE AND SILENCER"
section.
Clutch cable Disconnect at the engine side.
Radiator Refer to "RADIATOR" section.
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.
Ignition coil
Disconnect the CDI magneto lead.

5-16
FRONT FORK
FRONT FORK
REMOVING THE FRONT FORK
Order Part name Q'ty Remarks
Hold the machine by placing the suitable stand
under the engine.Refer to "HANDLING NOTE".
Front wheel Refer to "FRONT WHEEL AND REAR
WHEEL" section.
Front brake caliper Refer to "FRONT BRAKE AND REAR
BRAKE" section.
Number plateRefer to "SEAT, FUEL TANK AND SIDE
COVERS" section in the CHAPTER 4.
1Protector 1
2 Pinch bolt (upper bracket) 2 Only loosening.
3 Damper assembly 1Loosen when disassembling the front fork.
Refer to removal section.
4 Pinch bolt (lower bracket) 2 Only loosening.
5 Front fork 1