Page 122 of 414
5-13
EBU00947
Engine oil
Make sure the engine oil is at the specified level.
Fill with oil as necessary. (See pages 8-17 ~ 8-29
for details.)
Recommended oil:
Recommended engine oil classification:
API Service SE, SF, SG type or higher
-20˚ -10˚ 0˚
10˚20˚ 30˚40˚50˚C
10W/30
15W/4020W/4020W/50
10W/40
5W/30
U5LP61.book Page 13 Monday, August 27, 2001 3:49 PM
Page 274 of 414
8-19
NOTE:_ The engine oil should be between the minimum
and maximum level marks. _4. If the engine oil is below the minimum level
mark, add sufficient oil of the recommended
type to raise it to the correct level.NOTE:_ When adding oil, be careful not to overfill the en-
gine oil tank; the oil level rises faster starting from
the half-level-portion on the dipstick. _5. Insert the dipstick into the oil filler hole, and
then tighten the oil filler cap.CAUTION:_ Make sure that the oil filler cap is securely
tightened, otherwise oil may seep out when
the engine is running. _
U5LP61.book Page 19 Monday, August 27, 2001 3:49 PM
Page 282 of 414
8-27
11. 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 grade “CD” or higher. 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.
U5LP61.book Page 27 Monday, August 27, 2001 3:49 PM
Page 318 of 414

8-63 1. Brake fluid reservoir cover
2. Bolt (× 2)
1. Couvercle du réservoir de liquide de frein
2. Boulon (× 2)
1. Cubierta del depósito de líquido de frenos
2. Perno (× 2)
Rear
Arrière
Trasero
Observe these precautions:
When checking the fluid level, make sure the
top of the brake fluid reservoir is level.
Use only the designated quality brake fluid.
Otherwise, the rubber seals may deteriorate,
causing leakage and poor brake performance.
Refill with the same type of brake fluid. Mixing
fluids may result in a harmful chemical reaction
and lead to poor brake performance.
Be careful that water does not enter the brake
fluid reservoir when refilling. Water will signifi-
cantly lower the boiling point of the fluid and
may result in vapor lock.
Brake fluid may deteriorate painted surfaces or
plastic parts. Always clean up spilled fluid im-
mediately.
Have a Yamaha dealer check the cause if the
brake fluid level goes down. Recommended brake fluid: DOT 4
U5LP61.book Page 63 Monday, August 27, 2001 3:49 PM
Page 392 of 414
10-1
EBU00428
SPECIFICATIONS
MODEL YFM660R
Dimension:
Overall length
Overall width
Overall height
Seat height
Wheel base
Ground clearance
Minimum turning radius1,830 mm
1,100 mm
1,150 mm
860 mm
1,245 mm
265 mm
3,300 mm
Basic weight:
With oil and full fuel tank 193 kg
Engine:
Type
Cylinder arrangement
Displacement
Bore
× stroke
Compression ratio
Starting system
Lubrication systemLiquid-cooled, 4-stroke, SOHC
Forward inclined single cylinder
660 cm
3
100
× 84 mm
9.2 : 1
Electric starter
Dry sump
U5LP61.book Page 1 Monday, August 27, 2001 3:49 PM
Page 393 of 414
10-2
10
Engine oil:
Type
Recommended engine oil classification API Service SE, SF, SG type or higher
Quantity:
Periodic oil change
With oil filter replacement
Total amount1.9 L
1.95 L
2.3 L MODEL YFM660R
-20˚-10˚0˚
10˚20˚30˚40˚50˚C
10W/30
15W/4020W/4020W/50
10W/40
5W/30
CAUTION:Be sure to use motor oils that do not contain anti-
friction modifiers. Passenger car motor oils (often
labeled “ENERGY CONSERVING II”) contain anti-
friction additives which will cause clutch and/or
starter clutch slippage, resulting in reduced com-
ponent life and poor engine performance.
U5LP61.book Page 2 Monday, August 27, 2001 3:49 PM
Page 395 of 414
10-4
Gear ratio:
1st
2nd
3rd
4th
5th
Reverse31/12 (2.583)
30/18 (1.667)
27/21 (1.286)
22/21 (1.047)
19/21 (0.904)
33/25
× 25/18 (1.833)
Chassis:
Frame type
Caster angle
TrailSteel tube
8
°47 mm
Tire:
Type
Size: Front
Size: RearTubeless
AT21
× 7 - 10
AT20
× 10 - 9
Brake:
Front brake type
Operation
Rear brake type
OperationDual disc brake
Right hand operation
Single disc brake
Right foot operation
Suspension:
Front
RearDouble wishbone
Swingarm (link suspension)
Shock absorber:
Front
RearCoil spring/oil damper
Coil spring/gas-oil damper MODEL YFM660R
U5LP61.book Page 4 Monday, August 27, 2001 3:49 PM