What are RAVE Valves on a Sea-Doo? [+ Cleaning Guide]
Sea-Doo’s RAVE (or R.A.V.E. = Rotax Adjustable Variable Exhaust) valves were the special exhaust power valves on their 2-stroke Rotax engines. They were designed to change the size of the exhaust ports in order to widen the engine’s power band. Using RAVE valves ensured better low-end power and a higher top speed.
If you want to find out more about Sea-Doo’s RAVE valves and their maintenance, this post is for you.
We at JetDrift have compiled all you need to know under one roof!
What does a RAVE Valve do on a Sea-Doo?
In a nutshell, RAVE valves were designed to increase engine performance. They affected the engine in many ways, including:
- Changing the size of the exhaust ports
- Closing the secondary exhaust ports
- Raising the compression ratio
- Increasing low-end power
- Providing a higher peak RPM and top speed
RAVE valves looked like small guillotines mounted above the exhaust ports. Each 2-stroke RAVE Rotax engine utilized two valves (one valve per cylinder).
A round black plastic cap covered the valves with a red adjustment screw on top. The entire assembly was held together by a metal clip.
How do RAVE Valves Work on a Sea-Doo?
Simply put, RAVE valves were designed to enlarge the exhaust ports as engine speed increases. When the engine RPM decreased, the RAVE valves were lowered, making the exhaust ports smaller.
On the carbureted 787 Sea-Doo engine, the RAVE valves were opened by the exhaust pressure and closed by a spring. On these models, the valves were closed at idle speed but opened as engine RPM increased, and exhaust pressure overcame the spring’s tension.
In contrast, on fuel-injected Sea-Doos, the valves were electronically controlled, although exhaust pressure helped open the valves on these models as well.
Opening the RAVE valves caused a drop in the engine compression ratio. On the other hand, the larger exhaust ports allowed fumes to flow freely, while the tuned exhaust pipe returned a stronger pulse to compensate for the change in compression ratio.
Thanks to a better flow, the engine could rev higher, which resulted in more power and higher top speeds.
At lower RMPs, the RAVE valves closed, providing higher compression and a better low-end response.
Sea-Doo RAVE Engines
For your convenience, we’ve compiled production Sea-Doo RAVE engines into one chart:
|Rotax 787 RAVE||782||110||Carburetor|
|Rotax 787 RFI RAVE||782||110||Semi-direct fuel injection|
|Rotax 947 RAVE||951||130||Carburetor|
|Rotax 947 DI RAVE||951||130||Orbital direct injection|
It’s good to know that the RAVE valves on 951 engines were significantly larger, so the valves on 787 and 951 engines were not interchangeable.
Sea-Doo RAVE Valve Maintenance
How do You Know if the RAVE Valves Aren’t Working?
The most significant sign of the RAVE valves of your Sea-Doo not working is decreased engine performance and a lower top speed. If the valves can’t open, they restrict the flow of exhaust fumes, which prevents the engine from reaching its maximum RPM.
In most cases, RAVE valves get dirty and stick after a while, and their bellows, gaskets, and springs are also prone to aging.
To avoid these issues, you shouldn’t forget yearly maintenance of the RAVE valves!
How do You Test a RAVE Valve?
To test a RAVE valve, you have to cut a little “inspection window” into the black plastic cap. Remove the cap, drill a .5 – .8 inch hole into the surface, and then reassemble it. Fire up the engine, apply some throttle, and check how the valve is operating through the hole. Valve should open above a certain RPM (cca. 4500-5000).
If it doesn’t open, this indicates that your RAVE valves require a closer look!
(You can see the process on this video:)
How do You Clean a Rave Valve?
As a rule of thumb, each RAVE valve requires cleaning as part of annual maintenance to de-carbonize them. How is this done? All you need to do is disassemble the valve assembly and clean it with some carb cleaner and grit paper. Let’s look at the process step-by-step:
- To clean the RAVE valve, you have to remove and disassemble it first. It’s highly recommended that you note how the assembly came apart, as you will have to reassemble it in the same way.
- First, remove the spring clip on top and remove the plastic cap.
- The piston can be removed by turning it with a socket.
- On the bottom of the piston, you can find the rubber bellow secured by a tiny retaining spring. Remove these parts as well.
- Remove the two Allen screws that hold the base, then remove the gasket and the base.
- Pull the valve out (if it hasn’t already fallen out) and remove the small O-ring from the shaft.
- Clean off the build-up on the valve with some carburetor cleaner. If it’s really dirty, you can also use 400 grit paper.
- You may want to inspect the gasket and the rubber bellow for holes. If you see any damage, it’s time to replace these parts.
- Put the assembly back together and reassemble it in the engine.
Conclusion – What are RAVE Valves on a Sea-Doo?
As the name suggests, RAVE (Rotax Adjustable Variable Exhaust) valves are special exhaust valves on Rotax engines. They are also commonly called power valves. The main idea behind RAVE valves is to widen the engine’s power band, which ensures better low-end power and higher top speeds.
RAVE valves are actually small metal guillotines that partially cover the exhaust port.
At lower RPMs the valves stay closed, ensuring a higher compression ratio and a better lower-end response. At higher PRMs, the valves open and allow the engine to breathe better. This results in a higher peak RPM providing more HP and a higher top speed.
Carbed Rotax engines use exhaust pressure to control and operate RAVE valves, while on fuel-injected power sources, they are controlled electronically.
Like any other part of a Sea-Doo, RAVE valves require yearly inspections and maintenance. Dirty valves are prone to getting stuck, which restricts engine performance.
To prevent this issue, every RAVE valve has to be disassembled and cleaned annually!
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