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stingray719
Well-known member
When a mechanical check valve is used in the breather system, usually it is dependent on gravity to function. Mechanical check valves work well in watercraft, because a watercraft is either going to be right side up, or 180 degrees upside down. A snowmobile can be tipped over pretty much at any angle and often times they are tipped at an angle steep enough for oil to leak out. However it may not be a steep enough of an angle to activate a mechanical check valve.
The electric system actually has several functions
The first function is to get the engine shut down as soon as possible. While engine is running, there is positive air pressure escaping out the breather hose. If the sled is tipped on it's side at a steep enough of an angle, oil can flow over to the breather port in the oil tank. Once this happens the positive air flow (from the running engine) can actually pump the oil out of the tank under pressure.
The second function of an electric system is to simultaneously close the shut off valve while shutting down the engine. The shut off valve closes the breather to help prevent oil from escaping.
A third function on Viper/XF/M7000 sleds is the oil pump re-prime mode. Because the re-prime function uses pressure to feed oil to the supply port, it can be used at odd angles once the sled is rubber side down. This means that you don't necessarily have to have the sled on completely level ground for it to function.
The pump re-prime button can come in handy if you are in an area where you don't want to be in (such as stuck on a side of a very steep hill) and need to quickly re-prime the oil pump to get on your way!
To provide consistent and repeatable valve closing under all operating conditions on Viper/XF/M7000 sleds we use a ROVCM control module. Because the shut off valve is effectively about 170% stronger when a ROVCM is used in the circuit, the valve is much more resistant to oil/moisture residue that may accumulate in the breather system. This also reduces maintenance (valve cleaning) and in some cases even illuminates it.
Bill
The part Bill does not mention is a ball check valve in some areas that get a lot of moisture can freeze and pump all the oil out. I had a ball check I made for cheap on my Phazer and liked it, but a guy back east that did my mod had the ball freeze and pumped all his oil out and the limp home mode shut it off. He thinks it is a false reading and starts it and pins it and blows up his Phazer.
So I no longer suggest you do your own and suggest you buy the kit mentioned above.
Side note, the Viper can also have moisture in the breather system freeze and pump the oil out, I know a guy that happened to in the Midwest.
