Go carts can be complex racing carts or simple back yard projects. Many of the racing carts have pre built chassis that are design specific for racing. Most people will purchase a cart for racing instead of building one. There are three popular type of racing carts oval dirt carts, briggs and stratton and tecumseh type carts for pavement racing and shifter type pavement carts for faster road courses. Homebuilt carts are not so critical and can be built from steel tubing or even wood depending on the chassis required. The engine is usually a small four stroke engine such as used on a garden tractors or lawn mowers. If this type of an engine is used the transmission of power is usually a centrifugal clutch running to a sprocket on the drive axel. This limits the cart to be a one speed. Another option is to use a two stroke engine from a snowmobile or an off road bike. The high power and multi gear ratios of both vehicles make them both very fast drivetrains to use. You will want to use a very good brake set-up for one of these drivetrains. A cheap used snowmobile has everything except the chassis all integrated together and gives the cart far more power than it needs. The snowmobile transmission is variable and is fully automatic as it doesn’t need to be shifted. Shifter carts use the engine and transmission from an off road motorcycle. This requires the driver to shift but is also very effective and fast.