A Vespa is a fairly simple vehicle. The body of the scooter also acts as the frame, and is made out of pressed steel. Known as a monocoque frame, this gives a scooter a good ratio of strength and rigidity compared to its weight. This differs from motorcycles, which are built on a welded frame made of beams or tubes of metal. The engine is usually rear-mounted (some newer designs have the engine in the front), either beneath or behind the driver’s seat. It is covered by an engine cowling or simply enclosed within the frame/body. The engine may be off-centered, because in most scooter models the engine is connected directly to the rear axle. This eliminates the need for a belt or chain-driven system, reducing complexity and increasing reliability. The first Vespas used two-stroke engines, but today almost all scooters use four-stroke engines for lower emissions and greater fuel efficiency.
Rather than sitting astride the vehicle, a scooter’s driver sits on the seat much like sitting on a cushioned stool, with the feet flat on the floor of the frame directly in front of the driver. This allows women to drive Vespas while wearing a dress or a skirt (a major consideration when the Vespa was first designed, and certainly a factor for some drivers today). The front panel protects the driver’s legs from splashes. Storage space is usually included under the seat or on the front panel.
Part of the original Vespa design specification was the wheels be easy to remove for the average person, and that the scooter carry its own spare. Modern scooters don’t all carry spares, but most of them have kept the stub axle design that allows a scooter’s wheels to be removed much like a car tire. The wheel is fastened to the frame only on one side, as opposed to a motorcycle wheel, which is placed between two frame rails (a fork), and may be connected to the drive system, further complicating removal. Scooter wheels range from eight to 12 inches.
Early Vespa models had manual transmissions controlled by twisting the left handlebar. It was connected to the transmission by a series of rods, giving these models the nickname “Rods.” Twisting the right handlebar controlled the throttle, with thumb controls for the horn and lights. Modern Vespas (except for intentionally retro models) are known as “twist-n-go” scooters, because the transmission is a continuously variable automatic. The driver doesn’t have to worry about shifting gears and can simply twist the throttle control to accelerate. Handlebar mounted squeeze levers control braking, much like you’d find on a bicycle; steering controls are also similar to a bicycle or motorcycle.