engine YAMAHA YFZ450 2006 Repair Manual

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
5TG-9-62 8 5/13/05 1:48 PM Page 8-79

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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8-115
EBU05700
Cable inspection and lubrication
w
Inspect cables frequently and replace if dam-
aged. Corrosion can result when the outer
covering of control cables becomes dam-
aged. Cables can also become frayed or
kinked. Operation 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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8-149
EBU07240
Troubleshooting chart
Starting problems or poor
engine performance
2. Compression
Use the electric
starter to see if there
is compression.
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 weak.
Spark good.Ignition system normal.
No spark.
Ask a Yamaha dealer to inspect.
Adjust the spark plug gap
or replace the spark plug.
There is compresson.Compression normal.
Ask a Yamaha dealer to inspect.No compression.
4. Battery
Use the electric
starter
Engine turns over
quickly.Battery is good.
Check the connections, and charge the battery if necessary.Engine turns over
slowly
Check the fuel
flow.
1. Fuel
Check if there is
fuel in the fuel
tank.
There is fuel.Turn the fuel
cock to “OFF”.
Remove the
fuel hose from
the fuel cock.Turn the fuel cock
lever to “ON”.No fuel.Fuel cock clogged.
Some fuel.Turn the fuel cock
lever to “RES”.Restart the engine.
No fuel.Supply fuel.
Clean the fuel
cock.
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8-150
Engine overheating
NOTE:
If it is difficult to get the recommended coolant, tap water can be temporarily used, provided that it is
changed to the recommended coolant as soon as possible.
w
Wait for the engine and radiator to cool before removing the radiator cap. You could be burned
by hot fluid and steam blown out under pressure. Always put a thick rag over the cap when
opening. Allow any remaining pressure to escape before completely removing the cap.
Wait until the
engine has cooled.Check the coolant level in the
reservoir tank and/or radiator.
Level is OK.
Level is low, check the
cooling system for leakage.
No
leakage.
Leakage.Ask a Yamaha dealer
to inspect and repair
the cooling system.
Add coolant.
(See NOTE.)
Restart the engine. If the engine overheats
again, ask a Yamaha dealer to inspect and/or
repair the cooling system.
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9-1
EBU04180
CLEANING AND STORAGE
A. CLEANING
Frequent, thorough cleaning of your machine
will not only enhance its appearance but will
improve its general performance and extend the
useful life of many components.
1. Before cleaning the machine:
a. Block off the end of the exhaust pipe to
prevent water entry. A plastic bag and
strong rubber band may be used.
b. Make sure the spark plug and all filler caps
are properly installed.
2. If the engine case is excessively greasy,
apply degreaser with a paint brush. Do not
apply degreaser to the chain, sprockets or
wheel axles.
3. Rinse the dirt and degreaser off with a gar-
den hose. Use only enough pressure to do
the job.
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9-5
8. Automotive type wax may be applied to all
painted and chrome plated surfaces.
Avoid combination cleaner-waxes. Many
contain abrasives which may mar the paint
or protective finish.
When finished, start the engine and let it
idle for several minutes.
w
Wet brakes may have reduced stopping abili-
ty, increasing the chance of an accident.
Test the brakes after washing. Apply the
brakes several times at slow speeds to let
friction dry out the linings.
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9-7
EBU05260
B. STORAGE
Long term storage (60 days or more) of your
machine will require some preventive proce-
dures to guard against deterioration. After thor-
oughly cleaning the machine, prepare for stor-
age as follows:
1. Fill the fuel tank with fresh fuel and add
fuel stabilizer (if available).
NOTE:
Use of fuel stabilizer eliminates the need to
drain the fuel system. Consult a Yamaha dealer
if the fuel system is to be drained instead.
2. Remove the spark plug, pour about one
tablespoon of SAE 10W30 or 20W40
motor oil in the spark plug hole and rein-
stall the spark plug. Ground the spark plug
wire and turn the engine over several times
to coat the cylinder wall with oil.
3. Clean the drive chain thoroughly and lubri-
cate it. (See page 8-111.)
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