There are two versions of the Kawasaki KLX250S that most bikers will come into contact with. Both share the same engine as well as the same six-speed transmission system.  On level ground the KLX250S has a top speed of around 88mph, which is really good considering that the engine is primarily designed for dirt use. The first generation 250S is an extremely light bike. In fact, it weighs no more than a supermoto dirt bike even though it's classified as a dual-sport motorcycle and is therefore street legal. The liquid-cooled four-valve single DOHC engine is among the lightest in its class, and is the same engine that was mounted on Kawasaki's professional motocross bikes. It's not something that most people would see in a motorcycle designed for the road. Second generation 250S bikes use a special digital CDI ignition that's been redesigned from the original. They have a really impressive compression ratio of 11:1, which is actually quite tight considering the size of this bike. Second generation 250S models weigh around 16 lbs. more than first generation.