wheel YAMAHA YZ250F 2001 Service Manual

5 - 39
CHASFRONT FORK
4. Tighten:
lPinch bolt (upper bracket) 1
lPinch bolt (lower bracket) 2
ACHTUNG:CAUTION:
Tighten the lower bracket to specified
torque. If torqued too much, it may cause
the front fork to malfunction.
5. Install:
lBrake hose holder 1
lBrake caliper 2
lBolt (brake caliper) 3
NOTE:
Fit the brake hose holder cut a over the pro-
jection b on the front fork and clamp the brake
hose.
6. Install:
lBrake hose holder 1
lBolt (brake hose holder) 2
lProtector 3
lBolt (protector) 4
NOTE:
When installing the brake hose holder, pass
the brake hose 5 in front of the axle boss a,
then fit it into the hose groove b so that the
brake hose does not contact the nut (wheel
axle).
T R..23 Nm (2.3 m · kg, 17 ft · lb)
T R..20 Nm (2.0 m · kg, 14 ft · lb)
T R..23 Nm (2.3 m · kg, 17 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
7. Adjust:
lRebound damping force
NOTE:
Turn in the damping adjuster 1 finger-tight
and then turn out to the originally set position.

7 - 11
TUN
EC720000
CHASSIS
Selection of the secondary reduction ratio
(Sprocket)
Secondary
reduction =
ratio
reduction ratio>
lIt is generally said that the secondary gear
ratio should be reduced for a longer straight
portion of a speed course and should be
increased for a course with many corners.
Actually, however, as the speed depends on
the ground condition of the day of the race,
be sure to run through the circuit to set the
machine suitable for the entire course.
lIn actuality, it is very difficult to achieve set-
tings suitable for the entire course and some
settings may be sacrificed. Thus, the settings
should be matched to the portion of the
course that has the greatest effect on the
race result. In such a case, run through the
entire course while making notes of lap times
to find the best balance; then, determine the
secondary reduction ratio.
lIf a course has a long straight portion where
a machine can run at maximum speed, the
machine is generally set such that it can
develop its maximum revolutions toward the
end of the straight line, with care taken to
avoid the engine over-revving.
NOTE:
Riding technique varies from rider to rider and
the performance of a machine also vary from
machine to machine. Therefore, do not imitate
other rider’s settings from the beginning but
choose your own setting according to the level
of your riding technique.Standard secondary
reduction ratio48/13 (3.692)
Number of rear wheel sprocket teeth
Number of drive sprocket teeth
SETTING

7 - 12
TUNSETTING
EC72N000
Drive and driven sprockets setting parts
Part name Size Part number
Drive sprocket 1
(STD) 13T 9383B-13218
Rear wheel
sprocket
2 (STD)47T
48T
49T
50T
51T
52T5ET-25447-00
5ET-25448-00
5ET-25449-00
5ET-25450-00
5ET-25451-00
5ET-25452-00
EC721002
Tire pressure
Tire pressure should be adjust to suit the road
surface condition of the circuit.
lUnder a rainy, muddy, sandy, or slippery
condition, the tire pressure should be lower
for a larger area of contact with the road sur-
face.
lUnder a stony or hard road condition, the tire
pressure should be higher to prevent a flat
tire.
Standard tire pressure:
100 kPa (1.0 kg/cm2, 15 psi)
Extent of adjustment:
60 ~ 80 kPa
(0.6 ~ 0.8 kg/cm
2, 9.0 ~ 12 psi)
Extent of adjustment:
100 ~ 120 kPa
(1.0 ~ 1.2 kg/cm
2, 15 ~ 18 psi)

7 - 17
TUN
EC72B000
Rear suspension setting
The rear suspension setting should be made
depending on the rider’s feeling of an actual
run and the circuit conditions.
The rear suspension setting includes the fol-
lowing two factors:
1. Setting of spring preload
lChange the set length of the spring.
lChange the spring.
2. Setting of damping force
lChange the rebound damping.
lChange the compression damping.
EC72C001
Choosing set length
1. Place a stand or block under the engine
to put the rear wheel above the floor, and
measure the length a between the rear
wheel axle center and the rear fender
holding bolt.
2. Remove the stand or block from the
engine and with a rider astride the seat,
measure the sunken length b between
the rear wheel axle center and the rear
fender holding bolt.
3. Loosen the locknut 1 and make adjust-
ment by turning the spring adjuster 2 to
achieve the standard figure from the sub-
traction of the length b from the length
a.
Standard figure:
90 ~ 100 mm (3.5 ~ 3.9 in)
SETTING