2006 YAMAHA YFZ450 engine

8-59
8. Use the spark plug wrench in the owner’s
tool kit to remove the spark plug as shown.
Inspection
The spark plug is an important engine compo-
nent and is easy to inspect. The condition of the
spark plug can indicate the condition of the
engine.
The ideal color on the white insulator around the
center electrode is a medium-to-light tan color
for an ATV that is being ridden normally.
Do not attempt to diagnose such problems your-
self.
Instead, take the ATV to a Yamaha dealer. You
should periodically remove and inspect the
spark plug because heat and deposits will cause
the spark plug to slowly break down and erode.
If electrode erosion becomes excessive, or if
carbon and other deposits are excessive, you
should replace the spark plug with the specified
plug.
1. Spark plug wrench1. Clé à bougie1. Llave de bujía
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8-69
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.
w
Always use parts cleaning solvent to clean
the air filter element. Never use low flash
point solvents or gasoline to clean the air fil-
ter element because the engine could catch
fire or explode.
1. Wing bolt 2. Air filter element1. Boulon papillon 2.Élément du filtre à air1. Perno de aletas 2Elemento del filtro de aire
1. Air filter element 2. Frame
1. Élément du filtre à air 2.Armature1. Elemento del filtro de aire 2Bastidor
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8-73
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 ele-
ment 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 manifold fittings for an
airtight seal. Tighten all fittings securely to avoid
the possibility of unfiltered air entering the
engine.
cC
Never operate the engine with the air filter
element removed. This will allow unfiltered
air to enter the engine, causing rapid engine
wear and possible engine damage.
Additionally, operation without the air filter
element will affect carburetor jetting with
subsequent poor performance and possible
engine overheating.
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8-75
EBU02960
Carburetor adjustment
The carburetor is a vital part of the engine and
requires very sophisticated adjustment. Most
adjusting should be left to a Yamaha dealer who
has the professional knowledge and experience
to do so. However, the idling speed may be per-
formed by the owner as a part of the usual main-
tenance routine.
cC
The carburetor was set at the Yamaha facto-
ry after many tests. If the settings are dis-
turbed by someone without sufficient techni-
cal knowledge, poor engine performance and
damage may result.
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8-77
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,
resulting in improper fuel/air supply or engine
noise. To prevent this, the valve clearance must
be adjusted regularly. This adjustment however,
should be left to a professional Yamaha service
technician.Specified idle speed:
1,750–1,850 r/min
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8-79
EBU03070
Throttle lever adjustment
NOTE:
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.
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
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8-107
EBU15752
Adjusting the drive chain slack
1. Loosen the rear axle pinch bolts.
2. Insert a rod of a diameter of 8 mm and a
length of 10 cm into one of the holes in the
drive chain tensioner as shown.
3. Shift the transmission into the neutral posi-
tion.
4. To loosen the drive chain, push the ATV
forward, and to tighten the drive chain,
push the ATV backward.
cC
Improper drive chain slack will overload the
engine as well as other vital parts of the ATV
and can lead to chain slippage or breakage.
To prevent this from occurring, keep the
drive chain slack within the specified limits.
4
2
11
3
1. Rear axle pinch bolt (×4) 2. Rod
3. Drive chain tensioner 4. Hole (×3)
1. Boulon de pincement de 2. Tige
l’essieu arrière (×4)
3. Tendeur de chaîne de 4. Orifice (×3)
transmission
1. Perno de sujeción del 2. Barra
eje trasero (×4)
3. Tensor de la cadena de 4. Orificio (×3)
transmisión
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8-113
2. Wipe the drive chain dry.
3. Thoroughly lubricate the drive chain with a
special O-ring chain lubricant.
cC
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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