A new Smart Motor Generator, or SMG, silently starts the engine without using a starter motor and also reduces weight. Friction losses were further reduced by using roller-rocker-arm and forged piston for lower reciprocating mass and minimize vibration compared to cast pistons. This cooling effect is complemented by a piston cooler that sprays motor oil underneath the piston.

Despite not having liquid-cooling, Yamaha uses DiASil cylinder head liners that dissipate heat three times faster than steel. This was achieved by optimizing the valve angle design that enhances the tumble flow effect for better combustion of the air-fuel mixture, and a hemispherical combustion chamber that results in a higher compression ratio. The Gravis is powered by an air-cooled, single cylinder, sohc, 2 valve motor that features Yamaha’s Blue Core principle of extracting more power by using less fuel. The button below it unlocks the seat to access the underseat compartment with a 25 liter capacity, enough to fit a full face helmet. This can be accessed by pressing a button labelled ‘fuel’ next to the integrated key shutter. To make loading fuel much easier at the gas pumps, Yamaha placed the fuel filler lid behind the front apron, just below the left handlebar. This design not only frees up significant space under the seat, where the fuel tank are located on most scooters, it also shifts the center-of-gravity lower for better stability and weight distribution, while still having a genuine step through design. According to Yamaha the name Gravis was actually derived from the word gravity, the invisible force by which the weight of an object draws towards the center, which was probably used to describe the unusual placement of the Gravis’ fuel tank, which is under the footboard. But what exactly makes the Gravis any different from its existing lineup of excellent 125cc automatics? The answer is gravity.

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