Section 04 ENGINE (2-STROKE)
Subsection 04 (TOP END)
GENERAL
The 2-stroke ROTAX engine rotates counterclock-
wise seen from the rear (PTO flywheel).
The 717 and 787 RFI engines have a rotary valve
to control opening and closing of the intake. The
947 DI engines uses reed valves in the crankcase.
The 787 RFI and 947 DI engines are also equipped
with the RAVE system (Rotax Adjustable Variable
Exhaust).
CAUTION: No engine components can be inter-
changed between engines.
RAVE System
(Rotax Adjustable Variable Exhaust)
BASIC OPERATION
The RAVE valves change the height of the exhaust
port. The RAVE valve solenoid, which is controlled
by the MPEM, allows either positive crankcase
pressure (787 RFI engines) or a pressure from the
air compressor (947 DI engines) to inflate the bel-
lowsandopentheRAVEvalves.
On top of the RAVE, there is a red plastic ad-
justment knob. Turning the adjustment in or out
changes the preload on the return spring which,
in turn, will change the RPM at which the RAVE
valve opens and closes. On 947 DI engines, the
spring preload does not have a significant effect
on the valve operation.
787 RFI Engines
On these engines, the RAVE valves are controlled
by the Multi-Purpose Electronic Module (MPEM).
To open the RAVE valves, the MPEM activates a
solenoid which directs the positive pressure from
engine crankcase to the valves.
2
F06D3BA
13
1. Solenoid
2. Pressure hose from crankcase
3. To atmospheric pressure
NOTE: A check valve on the pressure line elimi-
nates the negative pressure from the crankcase.
To close the RAVE valves, the MPEM deactivates
the solenoid which blocks the crankcase positive
pressure. The RAVE valves are opened to the at-
mosphere.
3
F06D16A
2
1
4
5
RAVE VALVE OPENED
1. Pulse from crankcase
2. Check valve
3. Positive pressure to solenoid
4. Solenoid activated
5. Positive crankcase pressure to RAVE valves
102 smr2004-Complete Line Up
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