Bombardier SeaDoo 1998 factory shop manual, Page 79Get this manual
Section 04 ENGINE Subsection 05 (TOP END)
GENERAL
The 2-stroke ROTAX engine rotates counterclockwise seen from the rear (PTO flywheel)The 717 and 787 engines have rotary valve to control opening and closing of the intakeThe 947 engine uses reed valves in the crankcaseThe 787 and 947 engines are also equipped with the RAVE system (Rotax Adjustable Variable Exhaust)
Located above the exhaust port is guillotinetype slide valveThis rectangular valve is connected by shaft to diaphragm which is working against the return springTo the outside of the return spring is red plastic adjustment knobTurning 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-
CAUTION