2005 YAMAHA YFZ450 engine

8-67 1. Wing bolt 2. Air filter element
1. Boulon papillon 2.Élément du filtre à air
1. Perno de aletas 2. Elemento del filtro de aire
1. Air filter element 2. Frame
1.Élément du filtre à air 2. Armature
1. Elemento del filtro de aire 2. Bastidor
3. Remove the air filter element by removing the
wing bolt.
4. Remove the air filter element from its frame.
5. Wash the air filter element gently but thor-
oughly in solvent.
WARNING
_ Always use parts cleaning solvent to clean the
air filter element. Never use low flash point sol-
vents or gasoline to clean the air filter element
because the engine could catch fire or ex-
plode. _
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8-71
NOTE:_ The air filter element should be cleaned every 20–
40 hours. It should be cleaned and lubricated more
often if the machine is operated in extremely dusty
areas. Each time air filter element maintenance is
performed, check the air inlet to the air filter case
for obstructions. Check the air intake duct between
the air filter case and the carburetor and the mani-
fold fittings for an airtight seal. Tighten all fittings
securely to avoid the possibility of unfiltered air en-
tering the engine. _CAUTION:_ Never operate the engine with the air filter ele-
ment removed. This will allow unfiltered air to
enter the engine, causing rapid engine wear
and possible engine damage. Additionally, op-
eration without the air filter element will affect
carburetor jetting with subsequent poor per-
formance and possible engine overheating. _
U5TG61.book Page 71 Friday, April 2, 2004 11:28 AM

8-73
EBU02960
Carburetor adjustment
The carburetor is a vital part of the engine and re-
quires very sophisticated adjustment. Most adjust-
ing should be left to a Yamaha dealer who has the
professional knowledge and experience to do so.
However, the idling speed may be performed by
the owner as a part of the usual maintenance rou-
tine.CAUTION:_ The carburetor was set at the Yamaha factory
after many tests. If the settings are disturbed
by someone without sufficient technical
knowledge, poor engine performance and
damage may result. _
U5TG61.book Page 73 Friday, April 2, 2004 11:28 AM

8-75
EBU13970
Idle speed adjustment
A special tester is needed to check the engine
r/min on this model.
Therefore, take the ATV to a Yamaha dealer to
have the idle speed adjusted.
EBU03030
Valve clearance adjustment
The correct valve clearance changes with use, re-
sulting in improper fuel/air supply or engine noise.
To prevent this, the valve clearance must be ad-
justed regularly. This adjustment however, should
be left to a professional Yamaha service techni-
cian. Specified idle speed:
1,750–1,850 r/min
U5TG61.book Page 75 Friday, April 2, 2004 11:28 AM

8-77 1. Locknut 2. Adjusting bolt
a. Throttle lever free play
1. Contre-écrou 2. Boulon de réglage
a. Jeu du levier d’accélération
1. Contratuerca 2. Perno de ajuste
a. Juego libre de la palanca del acelerador
EBU03070
Throttle lever adjustmentNOTE:_ Adjust the engine idling speed before adjusting the
throttle lever free play. _1. Loosen the locknut.
2. Turn the adjusting bolt until the throttle lever
free play is 2–4 mm.
3. Tighten the locknut.
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8-109
2. Wipe the drive chain dry.
3. Thoroughly lubricate the drive chain with a
special O-ring chain lubricant.CAUTION:_ Do not use engine oil or any other lubricants
for the drive chain, as they may contain sub-
stances that could damage the O-rings. _
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8-111
EBU05700
Cable inspection and lubrication
WARNING
_ Inspect cables frequently and replace if dam-
aged. Corrosion can result when the outer cov-
ering of control cables becomes damaged.
Cables can also become frayed or kinked. Op-
eration of controls could be restricted, which
could cause an accident or injury. _Lubricate the inner cables and the cable ends. If
the cables do not operate smoothly, ask a Yamaha
dealer to replace them.
Recommended lubricant:
Engine oil
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8-147
EBU07240Troubleshooting chart
Starting problems or poor engine performance1. Fuel
Check if there is fuel
in the fuel tank.There is fuel.Turn the fuel cock
lever to “OFF”.No fuel.Fuel cock is
clogged.
Clean the
fuel cock. Some fuel.Turn the fuel cock
lever to “RES”.Restart the engine.
No fuel.Supply fuel.
2. Compression
Use the electric
starter to see if
there is compression.There is compression.
Compression normal.
No compression.Ask a Yamaha dealer to
inspect.
3. Ignition
Remove the
spark plug and
check the electrodes.WetWipe clean with dry cloth.
DryAttach spark plug cap and
ground to chassis.Use the
electric starter.Spark is good.Ignition system is
normal.
Spark is weak.
Adjust the spark plug gap
or replace the spark plug. No spark.
Ask a Yamaha dealer to
inspect. 4. Battery
Use the electric starter.Engine turns over
quickly.Battery is good.
Engine turns over
slowly.Check the battery lead connections,
and charge the battery if necessary.Check the
fuel flow.
Turn the fuel cock
lever to “ON”.
Remove the fuel hose
from the fuel cock.
U5TG61.book Page 147 Friday, April 2, 2004 11:28 AM