2006 YAMAHA YFZ450 check engine

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.
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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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8-77
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
5TG-9-62 8 5/13/05 1:48 PM Page 8-77

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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