engine YAMAHA YFM660R 2002 Workshop Manual

8-29
12. Start the engine, and then let it idle for sever-
al minutes while checking it for oil leakage. If
oil is leaking, immediately turn the engine off
and check for the cause.
13. Turn the engine off, and then check the oil
level and correct it if necessary.
U5LP61.book Page 29 Monday, August 27, 2001 3:49 PM

8-31 1. Coolant reservoir cap
2. Maximum level mark
3. Minimum level mark
1. Bouchon 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
EBU01015
Cooling system
1. Check the coolant level in the coolant reser-
voir when the engine is cold as the coolant
level will vary with engine temperature. The
coolant level should be between the maxi-
mum and minimum marks.
2. If the level is low, remove the coolant reser-
voir cap, and then add coolant or distilled wa-
ter 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 auto-
matic. It is switched on or off according to the
coolant temperature in the radiator.
_If your ATV overheats, see page 8-122 for details.Coolant reservoir capacity:
0.29 L
U5LP61.book Page 31 Monday, August 27, 2001 3:49 PM

8-33 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
EBU01024
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 under
pressure. Always put a thick rag over the cap
when opening. Allow any remaining pressure
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.
U5LP61.book Page 33 Monday, August 27, 2001 3:49 PM

8-37
Recommended antifreeze:
High quality ethylene glycol antifreeze
containing corrosion inhibitors for
aluminum engines.
Antifreeze and water mixing ratio:
1:1
Total amount:
1.3 L
Coolant reservoir capacity:
0.29 L
U5LP61.book Page 37 Monday, August 27, 2001 3:49 PM

8-39
CAUTION:_ Hard water or salt water is harmful to the en-
gine. You may use soft water if you cannot get
distilled water. _12. Install the radiator cap and the coolant reser-
voir cap.
13. Start the engine and let it idle for several min-
utes. 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 ra-
diator.
14. Check the coolant level in the reservoir. If it is
low, add coolant to the maximum level mark.
15. Start the engine and then check for coolant
leakage.NOTE:_ If any leakage is found, have a Yamaha dealer
check the cooling system. _16. Install the panel.
U5LP61.book Page 39 Monday, August 27, 2001 3:49 PM

8-41 1. Spark plug cap
1. Capuchon de bougie
1. Tapa de bujía
EBU00680
Spark plug inspection
Removal
1. Remove the spark plug cap.
2. Use the spark plug wrench in the tool kit to re-
move the spark plug as shown.
Inspection
The spark plug is an important engine component
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 a
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 elec-
trode erosion becomes excessive, or if carbon and
other deposits are excessive, you should replace
the spark plug with the specified plug.
U5LP61.book Page 41 Monday, August 27, 2001 3:49 PM

8-45 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 cleaningNOTE: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 fil-
ter case.1. Remove the seat. (See page 4-33 for seat re-
moval procedure.)
2. Remove the air filter case cover by unhook-
ing 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 ex-
plode.
U5LP61.book Page 45 Monday, August 27, 2001 3:49 PM

8-49 1. Hose
1. Flexible
1. Manguera
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 the filter element mainte-
nance is performed, check the air inlet to the filter
case for obstructions. Check the air cleaner rubber
joint to the carburetor and manifold fittings for an
airtight seal. Tighten all fittings securely to avoid
the possibility of unfiltered air entering the engine. CAUTION:
Never operate the engine with the air filter ele-
ment removed. This will allow unfiltered air to
enter, causing rapid engine wear and possible
engine damage. Additionally, operation with-
out the filter element will affect carburetor jet-
ting with subsequent poor performance and
possible engine overheating.
U5LP61.book Page 49 Monday, August 27, 2001 3:49 PM

8-51
EBU00296
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.
U5LP61.book Page 51 Monday, August 27, 2001 3:49 PM

8-53 1. Throttle stop screw
1. Vis de butée de papillon
1. Tornillo de tope del acelerador
EBU00301
Idle speed adjustmentNOTE:A diagnostic tachometer must be used for this pro-
cedure.1. Start the engine and warm it up for a few min-
utes at approximately 1,000 to 2,000 r/min.
Occasionally rev the engine to 4,000 to
5,000 r/min. The engine is warm when it
quickly responds to the throttle.
2. Connect the tachometer and set the idle to
the specified idling speed by adjusting the
throttle stop screw. Turn the screw in to in-
crease engine speed, and out to decrease
engine speed.
Specified idle speed:
1,450 ~ 1,550 r/min
U5LP61.book Page 53 Monday, August 27, 2001 3:49 PM