2001 YAMAHA YFM660R engine

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NOTE:
The air filter element should be cleaned every
20 ~ 40 hours. It should be cleaned and lubri-
cated more often if the machine is operated in
extremely dusty areas. Each time the filter ele-
ment maintenance 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. Tight-
en all fittings securely to avoid the possibility
of unfiltered air entering the engine.
CAUTION:
Never operate the engine with the air filter el-
ement removed. This will allow unfiltered air
to enter, causing rapid engine wear and possi-
ble engine damage. Additionally, operation
without the filter element will affect carbure-
tor jetting with subsequent poor performance
and possible engine overheating.
1. Hose
1. Flexible
1. Manguera

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EBU00296
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 expe-
rience to do so. However, the idling speed may
be performed by the owner as a part of the
usual maintenance routine.
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.

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1. Throttle stop screw
1. Vis de butée de papillon
1. Tornillo de tope del acelerador
EBU00301
Idle speed adjustment
NOTE:
A diagnostic tachometer must be used for this
procedure.
1. Start the engine and warm it up for a few
minutes 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
increase engine speed, and out to de-
crease engine speed.
Specified idle speed:
1,450 ~ 1,550 r/min

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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.
EBU00306
Reverse lock release cable adjustment
The reverse lock release cable stretches with
use, resulting in improper function. To prevent
this, the cable must be adjusted regularly. This
adjustment, however, should be left to a
Yamaha dealer.

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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
EBU00307
Throttle lever adjustment
NOTE:
Adjust the engine idling speed before adjust-
ing the throttle lever free play.
1. Loosen the locknut.
2. Turn the adjusting bolt until the throttle le-
ver free play is 3 ~ 5 mm.
3. Tighten the locknut.

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2. Wipe the drive chain dry.
3. Thoroughly lubricate the drive chain with
a special O-ring chain lubricant.
CAUTION:
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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Cable inspection and lubrication
WARNING
Inspect cables frequently and replace if dam-
aged. Corrosion can result when the outer
covering of control cables becomes damaged.
Cables can also become frayed or kinked. Op-
eration 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.
EBU00737
Brake and shift pedal/brake and clutch lever
lubrication
Lubricate the pivoting parts of each lever and
pedal.Recommended lubricant:
Engine oil
Recommended lubricant:
Lithium-soap-based grease
(all-purpose grease)

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Troubleshooting chart
Starting problems or poor engine performance
1. Fuel
Check if there is fuel
in the fuel tank.There is fuel.Turn the fuel cock
lever to “OFF”.No fuel.Fuel cock is
clogged.
Clean the
fuel cock. Some fuel.Turn the fuel cock
lever to “RES”.Restart the engine.
No fuel.Supply fuel.
2. Compression
Use the electric
starter to see if
there is compression.There is compression.
Compression normal.
No compression.Ask a Yamaha dealer to
inspect.
3. Ignition
Remove the
spark plug and
check electrodes.WetWipe clean with dry cloth.
DryAttach spark plug cap and
ground to chassis.Use the
electric starter.Spark is good.Ignition system is
normal.
Spark is weak.
Adjust the spark plug gap
or replace the spark plug. No spark.
Ask a Yamaha dealer to
inspect. 4. Battery
Use the electric starter.Engine turns over
quickly.Battery is good.
Engine turns over
slowly.Check the connections.Check the
fuel flow.
Turn the fuel cock
lever to “ON”.
Remove the fuel hose
from the fuel cock.