fuel YAMAHA YZ450F 2007 Owner's Manual

3 - 17
INSP
ADJ
PILOT SCREW ADJUSTMENT
7. Install:
Oil filler cap
8. Inspect:
Engine (for oil leaks)
Oil level
Refer to “ENGINE OIL LEVEL INSPEC-
TION”.
9. Check:
Oil pressure
Checking steps:
Slightly loosen the oil gallery bolt 1.
Start the engine and keep it idling until oil
starts to seep from the oil gallery bolt. If no
oil comes out after one minute, turn the
engine off so it will not seize.
Check oil passages, oil filter and oil pump
for damage or leakage.
Start the engine after solving the prob-
lem(s) and recheck the oil pressure.
Tighten the oil gallery bolt to specification.
T R..
Oil gallery bolt:
10 Nm (1.0 m  kg, 7.2 ft  lb)
PILOT SCREW ADJUSTMENT
1. Adjust:
Pilot screw 1
Adjusting steps:
NOTE:
To optimize the fuel flow at a smaller throttle
opening, each machine’s pilot screw has
been individually set at the factory. Before
adjusting the pilot screw, turn it in fully and
count the number of turns. Record this num-
ber as the factory-set number of turns out.
Turn in the pilot screw until it is lightly
seated.
Turn out the pilot screw by the factory-set
number of turns.
Pilot screw (example):
1-1/4 turns out

3 - 18
INSP
ADJIDLE SPEED ADJUSTMENT/
VALVE CLEARANCE ADJUSTMENT
EC35M021
IDLE SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it up.
2. Adjust:
Idle speed
VALVE CLEARANCE ADJUSTMENT
NOTE:
The valve clearance should be adjusted
when the engine is cool to the touch.
The piston must be at Top Dead Center
(T.D.C.) on compression stroke to check or
adjust the valve clearance.
1. Remove:
Seat
Fuel tank
Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section in the CHAPTER 4.
2. Remove:
Spark plug
Engine upper bracket
Hot starter plunger
Refer to “CARBURETOR” section in the
CHAPTER 4.
Cylinder head cover
Refer to “CAMSHAFTS” section in the
CHAPTER 4. Adjustment steps:
Adjust the pilot screw.
Refer to “PILOT SCREW ADJUSTMENT”
section.
Turn the throttle stop screw 1 until the
specified engine idling speed.
NOTE:
Using a digital engine tachometer for idle
speed adjustment, detect the engine idling
speed by bringing the sensing element c of
the engine tachometer close to the ignition
coil 2.
To increase idle speed
→
Turn the throttle stop screw
1 in
a.
To decrease idle speed
→
Turn the throttle stop screw
1 out
b.
Engine idling speed:
1,900 ~ 2,100 r/min
c2

3 - 43
INSP
ADJ
STEERING HEAD INSPECTION AND ADJUSTMENT
Tighten the ring nut 3 using ring nut
wrench 4.
NOTE:
Apply the lithium soap base grease on the
thread of the steering shaft.
Set the torque wrench to the ring nut
wrench so that they form a right angle.
Ring nut wrench:
YU-33975/90890-01403
T R..
Ring nut (initial tightening):
38 Nm (3.8 m  kg, 27 ft  lb)
Loosen the ring nut one turn.
Retighten the ring nut using the ring nut
wrench.
WARNING
Avoid over-tightening.
T R..
Ring nut (final tightening):
7 Nm (0.7 m  kg, 5.1 ft  lb)
Check the steering shaft by turning it lock
to lock. If there is any binding, remove the
steering shaft assembly and inspect the
steering bearings.
Install the plain washer 5, handle crown
6, plain washer 7, steering shaft nut 8,
handlebar 9, handlebar holder (upper) 0
and number plate A.
NOTE:
The handlebar holder (upper) should be
installed with the punched mark a for-
ward.
Install the handlebar so that the marks b
are in place on both sides.
Install the handlebar so that the projection
c of the handlebar holder (upper) is posi-
tioned at the mark on the handlebar as
shown.
Insert the end of fuel breather hose B into
the hole in the steering shaft.
CAUTION:
First tighten the bolts on the front side of
the handlebar holder (upper), and then
tighten the bolts on the rear side.

4 - 1
ENG
EC400000
ENGINE
EC4R0000
SEAT, FUEL TANK AND SIDE COVERS
Extent of removal:
1 Seat removal
2 Fuel tank removal
3 Side covers removal
4 Number plate removal
Extent of removal Order Part name Q’ty Remarks
SEAT, FUEL TANK AND SIDE
COVERS REMOVAL
Preparation for removal Turn the fuel cock to “OFF”.
Disconnect the fuel hose.
1Seat 1
2 Air scoop (left and right) 2
3 Bolt (fuel tank) 2
4 Fuel tank 1
5 Side cover (left) 1
Refer to “REMOVAL POINTS”. 6 Side cover (right) 1
7 Number plate 1
13
4
2
3
SEAT, FUEL TANK AND SIDE COVERS

4 - 2
ENG
REMOVAL POINTS
Side cover
1. Remove:
Bolt (side cover)
Side cover (left) 1
Side cover (right) 2
NOTE:
Draw the side cover downward to remove it
because its claws a are inserted in the air fil-
ter case.
Number plate
1. Remove:
Bolt (number plate)
Number plate 1
NOTE:
The projection a is inserted into the band of
the number plate. Pull the band off the pro-
jection before removal.
Remove the hot starter cable 2 and clutch
cable 3 from the cable guide b on the num-
ber plate.
The projection c on the under bracket is
inserted into the number plate. Remove the
number plate by pulling it off the projection.
ASSEMBLY AND INSTALLATION
Air scoop
1. Install:
Air scoop 1
Bolt (air scoop)
NOTE:
Put the portion a of the flap of the air filter
case on the inside of the air scoop.
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)
SEAT, FUEL TANK AND SIDE COVERS

4 - 3
ENGEXHAUST PIPE AND SILENCER
EC4S0000
EXHAUST PIPE AND SILENCER
Extent of removal:
1 Silencer removal
2 Exhaust pipe removal
Extent of removal Order Part name Q’ty Remarks
EXHAUST PIPE AND
SILENCER REMOVAL
Preparation for removal Side cover (right) Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
1 Bolt (clamp) 1 Only loosening.
2 Bolt [silencer (front)] 1
3 Bolt [silencer (rear)] 1
4 Collar 1
5 Silencer 1
6Clamp 1
7 Nut (exhaust pipe) 1
8 Bolt (exhaust pipe) 1
9 Exhaust pipe 1
10 Gasket 2
2
1
2

4 - 6
ENGRADIATOR
EC450001
RADIATOR
Extent of removal:
1 Radiator removal
Extent of removal Order Part name Q’ty Remarks
RADIATOR REMOVAL
Preparation for removal Drain the coolant. Refer to “COOLANT REPLACEMENT”
section in the CHAPTER 3.
Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Exhaust pipe Refer to “EXHAUST PIPE AND
SILENCER” section.
1 Panel 2
2Clamp 8
3 Radiator (right) 1
4 Hose 2 1
5 Hose 3 1
6 Hose 4 1
7 Pipe 2/O-ring 1/1
8 Radiator breather hose 1
9 Radiator (left) 1
10 Hose 1 1
11 Pipe 1/O-ring 1/1
1

4 - 9
ENGCARBURETOR
CARBURETOR
Extent of removal:
1 Carburetor removal
Extent of removal Order Part name Q’ty Remarks
CARBURETOR REMOVAL
Preparation for removal Fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Rear shock absorber Refer to “REAR SHOCK ABSORBER”
section in the CHAPTER 5.
1Band 1
2 TPS coupler 1
3 Throttle cable cover 1
4 Throttle cable 2
5 Clamp (air cleaner joint) 1 Loosen the screw (air cleaner joint).
6 Clamp (carburetor joint) 1 Loosen the screws (carburetor joint).
7 Hot starter plunger 1
8 Carburetor 1
9 Carburetor joint 1
1

4 - 12
ENGCARBURETOR
EC466020
HANDLING NOTE
CAUTION:
Do not loosen the screws {TPS (throttle
position sensor)}
1 except when changing
the TPS (throttle position sensor) due to
failure because it will cause a drop in
engine performance.
1
REMOVAL POINTS
Pilot screw
1. Remove:
Pilot screw 1
NOTE:
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.
INSPECTION
Carburetor
1. Inspect:
Carburetor body
Contamination → Clean.
NOTE:
Use a petroleum based solvent for cleaning.
Blow out all passages and jets with com-
pressed air.
Never use a wire.

4 - 22
ENGCAMSHAFTS
CAMSHAFTS
CYLINDER HEAD COVER
Extent of removal:
1 Cylinder head cover removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removalCYLINDER HEAD COVER
REMOVAL
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 Gasket 1
6 Timing chain guide (top) 1
1