Each of the major types of kart racing — sprint racing, road racing, and speedway racing — has several competition classes. These classes are determined by three factors: the driver’s age; the combined weight of the kart and driver; and the engine size and type.
In national competiton, a driver must be at least 9 years old for sprint and speedway racing and 12 years old for road racing. Generally, kart races have several junior classes for drivers under 16 and a number of senior classes for drivers 16 years and older.
The type of engine in the kart also determines several competition classes. Engine size is the chief factor, but there are other considerations as well. Additional classes separate single engines from double engines, engines with reed valves from those with rotary valves, and stock-appearing engines from modified engines. Stock-appearing engines come straight from the box and have not been altered at all. Modified engines are allowed some changes. Finally, there are open classes, which place no restrictions on the type of engine used.
A special class included in road racing is the Formula Kart Experimental (FKE) class, which began in 1967. The FKE class is one of only two classes in karting to have karts with bodies. Generally, Formula Kart Experimental, or Formula, karts have no limitations except for engine size. As a result, these karts show more variation than other karting classes do. Most Formula karts are hand-built, one-of-a-kind machines. They have metal or fiberglass bodies, and many sport colorful paint jobs.