Drive Belt - Yamaha MM700A Manual

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belt from moving to a higher speed position until the en-
gine speed is increased. If the primary sheave moves to a
faster ratio too soon, engine rpm will drop and the engine
will begin to bog down. For peak efficiency, the engine
should operate within its optimum peak power range, hi-
creasing secondary spring tension may prevent upshifting
too early. By not shifting up too soon, the engine should
continue to operate within its peak power range.
2. Decreasing secondary spring tension allows the belt to
move to a higher speed position at a lower engine rpm.
The engine does not operate efficiently if it is running
faster than its peak power range. Decreasing spring ten-
sion allows adjustment so the drive system shifts into a
higher ratio sooner to match the engine power.
The torque sensing cam angle will have more affect on
the shifting sequence under heavy load than the tension of
the release spring.
Torque Sensing Cam Angle
The secondary spring (14, Figure 6) and the angle of
the torque sensing cam on the spring seat (1 5 , Figure 6)
work together to control how easily the secondary sheave
shifts to a faster speed ratio. The buttons (1 1. Figure 6)
push against the cam (15, Figure 6) to move the sliding
sheave (10, Figure 6). If the cam angle is steep- the
sheaves will shift to a faster speed ratio sooner and will
not be as responsive to increases in load. Conversely, low
cam angles will exert more side pressure and will slow
shifts until the load is reduced and speeds are higher.

DRIVE BELT

The drive belt transmits power from the primary sheave
to the secondary sheave. The belt provides a vital link in
the operation and performance of the snowmobile. To en-
sure top performance, the primary sheave, drive belt and
secondary sheave must match each other and the snow-
mobile model. The correct size drive belt must be in-
stalled, because belt width and length are critical to proper
operation. Belt wear affects clutch operation and shifting
characteristics. Since normal wear changes the width and
length of the belt, make sure to frequently adjust it as de-
scribed in this chapter. See Table 2 for new drive belt
width.
With general use, there is no specific mileage or time
limit on belt life. Belt life is directly related to mainte-
nance and the type of snowmobile operation. Inspect the
belt at the intervals listed in Chapter Three. Early belt fail-
ure (200 miles or less) is abnormal. Determine the cause
to prevent subsequent damage.
Make sure to maintain the center-to-center distance
from the primary sheave to the secondary sheave and the
offset of the sheaves for good performance and long belt
life. Correct center-to-center distance ensures correct belt
tension and reduction ratio. The correct Yamaha align-
ment bar or equivalent is necessary for checking the off-
CHAPTER TEN