Page 368 of 456
8-97
EBU00303
Valve clearance adjustment
The correct valve clearance changes with use, re-
sulting in improper fuel/air supply or engine noise.
To prevent this, the valve clearance must be ad-
justed regularly. This adjustment however, should
be left to a professional Yamaha service techni-
cian.
EBU03050
Select lever safety system cable adjustment
The select lever safety system cable stretches
with use, resulting in improper function. To prevent
this, the cable must be adjusted regularly. This ad-
justment, however, should be left to a Yamaha
dealer.
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8-145
EBU00413
Troubleshooting
Although Yamaha machines receive a rigid in-
spection before shipment from the factory, trouble
may occur during operation.
Any problem in the fuel, compression, or ignition
systems can cause poor starting and loss of pow-
er. The troubleshooting chart describes a quick,
easy procedure for making checks. If your ma-
chine requires any repair, take it to a Yamaha
dealer.
The skilled technicians at a Yamaha dealership
have the tools, experience, and know-how to prop-
erly service your machine. Use only genuine
Yamaha parts on your machine. Imitation parts
may look like Yamaha parts, but they are often in-
ferior.
Consequently, they have a shorter service life and
can lead to expensive repair bills.
WARNING
Do not smoke when checking the fuel system.
Fuel can ignite or explode, causing severe in-
jury or property damage. Make sure there are
no open flames or sparks in the area, including
pilot lights from water heaters or furnaces.
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8-147
EBU00724Troubleshooting chart
Starting problems or poor engine performance1. 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 the 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 battery lead connections,
and charge the battery if necessary.Check the
fuel flow.
Turn the fuel cock
lever to “ON”.
Remove the fuel hose
from the fuel cock.
U2C660.book Page 147 Monday, April 11, 2005 10:29 AM
Page 430 of 456
9-7
EBU00427
B. STORAGE
Long term storage (60 days or more) of your ma-
chine will require some preventive procedures to
guard against deterioration. After thoroughly
cleaning the machine, prepare for storage as fol-
lows:
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 ta-
blespoon of SAE 10W30 or 20W40 motor oil
in the spark plug hole and reinstall the spark
plug. Ground the spark plug wire and turn the
engine over several times to coat the cylinder
wall with oil.
3. Lubricate all control cables.
4. Block up the frame to raise all wheels off the
ground.
U2C660.book Page 7 Monday, April 11, 2005 10:29 AM
Page 434 of 456
10-1
EBU00428
1-SPECIFICATIONS
Model YFM66FA
Dimensions:
Overall length 2,085 mm
Overall width 1,150 mm
Overall height 1,210 mm
Seat height 880 mm
Wheelbase 1,275 mm
Ground clearance 275 mm
Minimum turning radius 3,200 mm
Basic weight:
With oil and full fuel tank 290 kg
Noise and vibration level:
Noise level (77/311/EEC) (for Europe) 80 dB (A)
Vibration on seat (EN1032, ISO5008) (for Europe) Not exceed 0.5 m/s
2
Vibration on handlebar (EN1032, ISO5008)
(for Europe) 2.8 m/s
2
Engine:
Engine type Liquid-cooled 4-stroke, SOHC
Cylinder arrangement Forward-inclined single cylinder
Displacement 660 cm
3
Bore
× stroke 100
× 84 mm
U2C660.book Page 1 Monday, April 11, 2005 10:29 AM
Page 436 of 456
10-3
Engine oil:
Quantity:
Without oil filter cartridge replacement 1.9 L
With oil filter cartridge replacement 2.0 L
Final gear case oil:
Type SAE80 API GL-4 Hypoid gear oil
Quantity 0.25 L
Differential gear case oil:
Type SAE80 API GL-4 Hypoid gear oil
Quantity 0.28 L
Radiator capacity (including all routes): 1.80 L
Air filter: Wet element
Fuel:
Type Unleaded gasoline only
For Europe: Regular unleaded gasoline only with a
research octane number of 91 or higher
Fuel tank capacity 20 L
Fuel reserve amount 3.5 L
Carburetor:
Type / quantity BSR42 / 1
Manufacturer MIKUNIModel YFM66FA
U2C660.book Page 3 Monday, April 11, 2005 10:29 AM
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