Chapter 4. Power Train; Sheave Alignment; Clutch Tuning - Yamaha BR250F Service Manual

POWER TRAIN
4-1.
SHEAVE ALIGNMENT
1. Sheave distance: 2. Sheave offset:
266 ±2 mm (10.47 ±O.OS in) 11 ± 3 mm (0.43 ± 0.12 in)
1. Using the sheave gauge, check the sheave
offset. If the gauge does not contact the
primary and secondary sheaves at the
four indicated points, the sheave offset is
incorrect.
2. Check the sheave center-to-center
distance.
4-1
3. If either the center-to-center distance or
the offset is not within specification,
check the engine mounts. If the engine
has been mounted correctly, the engine
mounting bracket, the frame, or both are
bent. Replace as required.
Sheave gauge: TLS-9091O-47-02 (U.S.A.)
90890-01702
Center-to-center:
266
±
2 mm (10.47
±
0.08 in)
Sheave offset:
11
±
3 mm (0.43
±
0.12 in)
4-2. CLUTCH
TUNING
The clutch may require tuning depending
upon the area of operation and the desired
handling characteristics. The clutch can be
tuned by changing engagement & shifting
rpm.
Clutch engagement rpm is defined as the
engine speed where the machine first begins
to move from a complete stop.
Shifting rpm is the engine speed when the
machine passes a point 200 ~ 300 m (650 ~
1000
ft)
from the starting position after the
machine has been started at full-throttle from
a dead stop.
Normally, when a machine reaches shift rpm,
the vehicle speed increases but the engine
speed remains nearly constant. Under un-
favorable conditions, however (wet snow, icy
snow, hills, or rough terrain), engine speed
can decrease after the engine has reached
shifting rpm.