Original sentence: Most are still air-cooled (forced with a fan in some cases) but water-cooling is becoming increasingly popular.The final drive of scooters is much shorter than that of regular motorcycles and is contained within the engine casings in an oil-bath, this design is only suitable for machines with small wheels
Edited sentence: 5 cylinder radial engines, either mouted conventionaly with the crank spinning, or as true rotaries, mounted in one of the wheels, with the crank stationary and the rest of the engine revolving (taking the wheel with it) like old propeller planes.A few oddities have used i.Suzuki made some Air/Oil cooled engines before switcing to water.The final drive of scooters is much shorter than that of regular motorcycles and is contained within the engine casings in an oil-bath, this design is only suitable for machines with small wheels, or is fully automatic using belts and pulleys, ala DAF variomatic cars.Vectrix make a full sized electric scooter now that is comparable to mid size petrol scooters.some are still air-cooled (forced with a fan in some cases) but water-cooling is now the norm