2001 YAMAHA YFM660R engine

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10. Add sufficient oil of the recommended
type to raise it to the correct level, and
then install and tighten the oil tank filler
cap.
CAUTION:
In order to prevent clutch slippage (since
the engine oil also lubricates the clutch),
do not mix any chemical additives with
the oil or use oils of a higher grade than
“CD”. In addition, do not use oils labeled
“ENERGY CONSERVING II” or higher.
Make sure that no foreign material enters
the crankcase. Recommended engine oil:
See page 10-2.

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11. Start the engine, and then let it idle for
several minutes while checking it for oil
leakage. If oil is leaking, immediately turn
the engine off and check for the cause.
12. Turn the engine off, and then check the oil
level and correct it if necessary.

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EBU00783
Cooling system
1. Check the coolant level in the coolant res-
ervoir when the engine is cold as the cool-
ant level will vary with engine temperature.
The coolant level should be between the
maximum and minimum marks.
2. Remove the coolant reservoir cap, and
then add coolant or distilled water to raise
it to the specified level.
CAUTION:
Hard water or salt water is harmful to the en-
gine. You may use soft water if you can’t get
distilled water.
NOTE:
If water is added, have a Yamaha dealer
check the antifreeze content of the coolant
as soon as possible.
The radiator fan operation is completely au-
tomatic. It is switched on or off according to
the coolant temperature in the radiator.
If your ATV overheats, see page 8-120 for details.Coolant reservoir capacity:
0.29 L
1. Coolant reservoir cap
2. Maximum level mark
3. Minimum level mark
1. Cache du vase d’expansion
2. Repère de niveau maximum
3. Repère de niveau minimum
1. Tapa del depósito de líquido refrigerante
2. Marca de nivel máximo
3. Marca de nivel mínimo

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Changing the coolant
WARNING
Wait for the engine and radiator to cool before
removing the radiator cap. You could be
burned by hot fluid and steam blown out un-
der pressure. Always put a thick rag over the
cap when opening. Allow any remaining pres-
sure to escape before completely removing
the cap.
1. Place the ATV on a level surface.
2. Remove panel A. (See page 8-15 for panel
removal and installation procedures.)
3. Place a container under the engine, and
then remove the coolant drain bolt.
4. Remove the radiator cap.
5. Remove the coolant reservoir cap.
1. Coolant drain bolt
1. Boulon de vidange du liquide de refroidissement
1. Perno de drenaje de refrigerante
1. Radiator cap
1. Bouchon de radiateur
1. Tapa del radiador

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Recommended antifreeze:
High quality ethylene glycol antifreeze
containing corrosion inhibitors for alumi-
num engines.
Antifreeze and water mixing ratio:
1:1
Total amount:
1.3 L
Coolant reservoir capacity:
0.29 L

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CAUTION:
Hard water or salt water is harmful to the en-
gine. You may use soft water if you cannot get
distilled water.
11. Install the radiator cap.
12. Start the engine and let it idle for several
minutes. Stop the engine, and then check
the coolant level in the radiator. If it is low,
add more coolant until it reaches the top
of the radiator.
13. Fill the coolant reservoir with coolant up
to the maximum level.
14. Install the coolant reservoir cap and check
for coolant leakage.
NOTE:
If any leakage is found, have a Yamaha dealer
check the cooling system.
15. Install the panel.

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Spark plug 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.
For example, a very white center electrode por-
celain color could indicate an intake air leak or
carburetion problem for that cylinder. Do not
attempt to diagnose such problems yourself.
Instead, take the machine 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,
you should replace the spark plug with one of
the proper type.
Standard spark plug:
DPR8EA-9 (NGK)

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1. Check hose
1. Flexible de contrôle
1. Manguito de comprobación
1. Air filter case cover 2. Holder (× 6)
1. Couvercle du boîtier de filtre à air 2. Support (× 6)
1. Tapa de la caja del filtro 2. Soporte (× 6)
EBU00818
Air filter element cleaning
NOTE:
There is a check hose at the bottom of the air
filter case. If dust or water collects in this hose,
empty the hose and clean the air filter element
and air filter case.
1. Remove the seat. (See page 8-15 for seat
removal procedure.)
2. Remove the air filter case cover by un-
hooking the holders.
3. Remove the air filter element and remove
it from its frame.
4. Wash the element gently but thoroughly
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 explode.