16
At high RPM, the exhaust valves are raised.
This creates a “high port” exhaust design
calibrated to provide maximum perfor-
mance at high RPM.
NOTE: The RPM ranges will vary
from model to model.
NOTE: If the servomotor cycles
three times and then shuts down, the
exhaust valve cables are not adjusted
correctly. The exhaust valves may also
be sticking.
NOTE: Take the snowmobile to an
authorized Yamaha Snowmobile dealer
for this service. This service is at the
discretion and expense of the snow-
mobile owner.
Exhaust-Controlled
Timing (ECT) System
This system automatically adjusts the ignition
timing to provide maximum performance
through a variety of operating conditions. The
ECM receives input on engine RPM (demand)
and exhaust pipe temperature (engine condi-
tion) and adjusts the ignition timing accord-
ingly. This system is not adjustable and is
maintenance free.
If a system fault is suspected, use an ohm-
meter to check continuity of the exhaust pipe
temperature sensor located in the expansion
chamber. A reading of either 0 ohm or infin-
ity indicates a failed sensor.
NOTE: A disabled ECT system WILL
NOT cause engine damage; however, a
failed ECT system will have slower throt-
tle response and may produce slightly
less top-end performance.
