Page 110 of 426
4-39 1. Spring preload adjusting nut
2. Locknut 3. Special wrench
1.Écrou de réglage de la précontrainte de ressort
2. Contre-écrou 3. Clé spéciale
1. Tuerca de ajuste de precarga del resorte
2. Contratuerca 3. Llave especial
A. Spring length
A. Longueur du ressort
A. Longitud del muelle
Adjust the spring preload as follows.
1. Loosen the locknut.
2. Turn the adjusting nut in direction
a to in-
crease the spring preload and in direction
b
to decrease the spring preload.
3. The length of the spring (installed) changes
1.5 mm per turn of the adjusting nut.NOTE:_ A special wrench can be obtained at a Yamaha
dealer to make this adjustment. _4. Tighten the locknut to the specified torque.CAUTION:_ Always tighten the locknut against the adjust-
ing nut, then tighten it to the specified torque. _
Measurement
A:
Installed length:
Minimum (hard): 232 mm
Standard: 240 mm
Maximum (soft): 247 mm
Tightening torque:
42 Nm (4.2 m·kgf)
U5LP63.book Page 39 Monday, March 10, 2003 2:06 PM
Page 118 of 426

5-1
EBU00113
PRE-OPERATION CHECKS
Before using this machine, check the following points:
ITEM ROUTINE PAGE
Front brakeCheck operation, lever free play, fluid level and fluid leakage.
Fill with DOT 4 brake fluid if necessary.5-5–5-7,
8-63–8-71
Rear brakeCheck operation, fluid level and fluid leakage.
Fill with DOT 4 brake fluid if necessary.5-5–5-7,
8-63–8-69, 8-73
ClutchCheck operation, condition and lever free play. 8-81
Parking brakeCheck operation, condition and cable length. 8-75–8-77
FuelCheck fuel level.
Fill with fuel if necessary.5-9–5-11
Engine oilCheck oil level.
Fill with oil if necessary.5-13–5-15,
8-17–8-31
Coolant reservoirCheck coolant level in reservoir.
Fill with coolant if necessary.5-17–5-19,
8-33–8-43
Drive chainCheck chain slack and condition.
Adjust if necessary.5-19, 8-83–8-89
ThrottleCheck for proper throttle cable operation and free play. 5-21, 8-59
Wheels and tiresCheck tire pressure, wear and damage.5-23–5-29,
8-99–8-101
Fittings and fastenersCheck all fittings and fasteners. 5-21
Lights and switchesCheck for proper operation.5-21, 8-79,
8-111–8-121
U5LP63.book Page 1 Monday, March 10, 2003 2:06 PM
Page 338 of 426
8-75 1. Locknut 2. Adjusting bolt
A. Cable length
1. Contre-écrou 2. Boulon de réglage
A. Longueur de câble
1. Contratuerca 2. Perno de ajuste
A. Longitud del cable
1. Locknut 2. Adjusting bolt
1. Contre-écrou 2. Boulon de réglage
1. Contratuerca 2. Perno de ajuste
EBU01192
Parking brake adjustment
Parking brake adjustment may be required if the
parking brake does not hold properly. The cable
length
A should be adjusted to 64–68 mm.
1. Fully loosen the locknut and the adjusting bolt
at the clutch lever.
2. Loosen the locknut and the adjusting bolt at
the rear brake caliper.
3. Turn the adjusting bolt at the clutch lever in
direction
a to increase the cable length or in
direction
b to decrease the cable length.NOTE:_ If the cable cannot be adjusted to specification,
consult a Yamaha dealer. _4. Tighten the locknut at the clutch lever.
U5LP63.book Page 75 Monday, March 10, 2003 2:06 PM
Page 404 of 426
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
U5LP63.book Page 1 Monday, March 10, 2003 2:06 PM