2006 YAMAHA YZ450F light

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):
2-1/8 turns out

3 - 45
INSP
ADJ
LUBRICATION
LUBRICATION
To ensure smooth operation of all compo-
nents, lubricate your machine during setup,
after break-in, and after every race.
1All control cable
2Clutch lever pivot
3Shift pedal pivot
4Footrest pivot
5Throttle-to-handlebar contact
6Drive chain
7Tube guide cable winding portion
8Throttle cable end
9Clutch cable end
0Hot starter cable endÈUse Yamaha cable lube or equivalent on these
areas.
ÉUse SAE 10W-30 motor oil or suitable chain
lubricants.
ÊLubricate the following areas with high quality,
lightweight lithium-soap base grease.
CAUTION:
Wipe off any excess grease, and avoid get-
ting grease on the brake discs.
AAA
AAB
CC

3 - 46
INSP
ADJ
ELECTRICAL/SPARK PLUG INSPECTION
EC370000
ELECTRICAL
EC371001
SPARK PLUG INSPECTION
1. Remove:
Spark plug
2. Inspect:
Electrode 1
Wear/damage → Replace.
Insulator color 2
Normal condition is a medium to light tan
color.
Distinctly different color → Check the
engine condition.
NOTE:
When the engine runs for many hours at low
speeds, the spark plug insulator will become
sooty, even if the engine and carburetor are in
good operating condition.
3. Measure:
Plug gap a
Use a wire gauge or thickness gauge.
Out of specification → Regap.
Spark plug gap:
0.7 ~ 0.8 mm (0.028 ~ 0.031 in)
4. Clean the plug with a spark plug cleaner if
necessary.
5. Tighten:
Spark plug
NOTE:
Before installing a spark plug, clean the gas-
ket surface and plug surface.
Finger-tighten a the spark plug before torqu-
ing to specification b.
T R..13 Nm (1.3 m · kg, 9.4 ft · lb)

3 - 47
INSP
ADJ
IGNITION TIMING CHECK
IGNITION TIMING CHECK
1. Remove:
Timing plug 1
2. Attach:
Timing light
Inductive tachometer
To the ignition coil lead
(orange lead 1).
Timing light:
YM-33277-A/90890-03141
3. Adjust:
Engine idling speed
Refer to “IDLE SPEED ADJUSTMENT”.
4. Check:
Ignition timing
Visually check the stationary pointer a is
within the firing range b on the rotor.
Incorrect firing range → Check rotor and
pickup assembly.
5. Install:
Timing plug

4 - 4
ENGEXHAUST PIPE AND SILENCER
INSPECTION
Exhaust pipe and silencer
1. Inspect:
Gasket 1
Damage → Replace.
1
Silencer fiber replacement
1. Remove:
Rivet (front) 1
Inner pipe 2
CAUTION:
Take care not to damage the rivet fitting
holes (ø4.9 mm) a in removal.
NOTE:
Pull out the inner pipe while lightly tapping the
stay b on the silencer using a soft hammer.
2. Replace:
Fiber 1
a
1
2
1
b
1
3. Install:
Inner pipe 1
Rivet (front) 2
NOTE:
Apply heat resistant sealant along the plate
edge a on the inside of the silencer and also
along the silencer edge b as shown.
Take care not to allow the fiber out of place
when installing the inner pipe.
2
1
a
a
b

4 - 18
ENGCARBURETOR
11. Install:
Needle valve 1
Float 2
Float pin 3
NOTE:
After installing the needle valve to the float,
install them to the carburetor.
Check the float for smooth movement.
12. Install:
Pilot screw 1
Spring 2
Washer 3
O-ring 4
Note the following installation points:
Turn in the pilot screw until it is lightly
seated.
Turn out the pilot screw by the number of
turns recorded before removing.
Pilot screw (example):
2-1/8 turns out
13. Install:
O-ring
Leak jet 1
Float chamber 2
Bolt (float chamber) 3
Cable holder (throttle stop screw cable)
4
Hose holder (carburetor breather hose)
5

4 - 20
ENGCARBURETOR
Accelerator pump timing adjustment
Adjustment steps:
NOTE:
In order for the throttle valve height a to
achieve the specified value, tuck under the
throttle valve plate 1 the rod 2 etc. with the
same outer diameter as the specified value.
Throttle valve height:
1.25 mm (0.049 in)
Fully turn in the accelerator pump adjust-
ing screw 3.
Check that the link lever 4 has free play
b by pushing lightly on it.
Gradually turn out the adjusting screw
while moving the link lever until it has no
more free play.
Carburetor installation
1. Install:
Carburetor joint 1
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
2. Install:
Carburetor 1
NOTE:
Install the projection a between the carburetor
joint slots.
3. Install:
Hot starter plunger 1
1
T R..2 Nm (0.2 m · kg, 1.4 ft · lb)

4 - 27
ENGCAMSHAFTS
Decompression system
1. Check:
Decompression system
Checking steps:
Check that the decompressor cam 1
moves smoothly.
Check that the decompressor lever pin 2
projects from the camshaft.
Timing chain tensioner
1. Check:
While pressing the tensioner rod lightly
with fingers, use a thin screwdriver 1
and wind the tensioner rod up fully clock-
wise.
When releasing the screwdriver by press-
ing lightly with fingers, make sure that the
tensioner rod will come out smoothly.
If not, replace the tensioner assembly.
ASSEMBLY AND INSTALLATION
1. Install:
Exhaust camshaft 1
Intake camshaft 2
Installation steps:
Turn the crankshaft counterclockwise until
the “I” mark a on the rotor is aligned with
the stationary pointer b on the crankcase
cover.
NOTE:
Apply the molybdenum disulfide oil on the
camshafts.
Apply the engine oil on the decompression
system.