from rave valve notes stored ......
For a 2-stroke-cycle engine to have high power capacity at high crankshaft speeds, a high volumetric or breathing efficiency is required and the fresh charge losses must be minimized. The result is achieved by opening the exhaust port early and utilizing the resonant effects of the tuned exhaust system to control fresh charge losses.
When an engine of this design is run at a high speed, efficiency falls off quickly. The relatively high exhaust port effectively shortens the useful power stroke and because the exhaust system is tuned for maximum power, there is a large increase of fresh charge losses at lower speeds. As a result, the torque decreases along with a dramatic increase of the specific fuel consumption. Higher torque along with lower fuel consumption can be obtained at lower engine speeds if the time the exhaust port is open is shortened.
Bombardier-Rotax has patented a remarkably simple system to automatically change the exhaust port height based on pressure in the exhaust system.
Located above the exhaust port is a guillotine-type slide valve. This rectangular valve is connected by a shaft to a diaphragm which is working against a return spring. Two small passages in the cylinder just outside the exhaust port allow exhaust gas pressure to reach the diaphragm.
To the outside of the return spring is a red plastic adjustment knob. Turning the adjustment in or out changes the preload on the return spring which, in turn, will change the RPM at which the R.A.V.E. valve opens and closes. As the throttle is opened and the engine begins producing more power, the pressure against the diaphragm will overcome the pressure of the return spring and the R.A.V.E. valve will open.
The R.A.V.E. valve does not allow an engine to make higher peak horsepower than an engine not so equipped, it can however make moving the peak horsepower higher practical, because of its effect on the rest of the power curve.
R.A.V.E. Valve Adjustment
The actual R.A.V.E. valves are contained within the 2 black caps you have atop your 2 cylinders. There is a water regulator with a R.A.V.E. type adjustment cap on it. Most have found that screwing this all the way in, creates the best performance. This doesn't regulate the water actually, but just how much pressure can be put on the regulator inside the cap before it does regulate the water. Here's a quick guide to adjusting them for optimum performance:
For acceleration: Cylinder R.A.V.E valves DOWN
For top speed: Cylinder R.A.V.E. valves UP
Stock 95/96 Engines: Cylinder R.A.V.E. valves UP
Stock 97 Engines: Cylinder R.A.V.E. valves DOWN
You will not gain more MPH, RPMs, or horsepower by changing the position of your valves, but you will change the powerband from "Point A" to "Point B". On 1995/1996 800 Engines, put your red cap flush with the top of the cap. On 1997 800 Engines, put the red cap all the way in (Don't force it all the way down, it does have a stop a little past halfway which is down). Due to the different impellers and ignition curves from the 95/96 and the 97 800 engines. Sea-Doo recommends this for maximum performance out of your engine. The 1997 800 Engine is actually more towards top end. This is apparent in the SPX which is .4 MPH faster than the 96 XP. Thus to compensate for the small loss in bottom end, they changed the powerband a little bit to get that back.
leave waterbox flush, should do it ok
