The layout used in Yamaha 4-stroke snowmobiles is a result of designing engines specifically for use in a sled. Turning the cylinder-head / exhaust to face the rear creates a straighter exhaust path which increases horsepower. It also moves engine and exhaust system weight closer to the center of the chassis for improved handling through centralized mass (moment of inertia). All Yamaha 4-stroke snowmobiles leverage this design.
Yamaha's Genesis line up consists of the:
Genesis Extreme (4-stroke RX series engine)
The new 150-horsepower class, fuel injected, Genesis Extreme FI, double overhead cam 4-cylinder engine is charged through a 20-valve cylinder head to produce unequalled torque with lightning quick throttle response and amazing 4-stroke power on top.
Genesis 120 (4-Stroke RS series triple)
For an in-depth look into Yamaha's four-stroke Genesis 120, read the article from Motoneige Québec, November 2004: ENGINES : THE EVOLUTION CONTINUES...text by Michel Garneau.
Our Genesis 120-horsepower class double overhead cam 12-valve triple (four valves per cylinder) extracts a bunch of torque and howling horsepower from a light, narrow, low center of gravity engine.
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Yamaha 4-stroke engine