Racing karts use small 2-stroke or 4-stroke engines.
The kart engines are developed and built by dedicated manufacturers. These can develop from about 4 hp to 7 hp for a single-cylinder 60 cc unit to 90 hp for a twin 250 cc. The most popular categories worldwide are those using the deep groove ball bearing as crankshaft support. SKF recently has developed a new roller bearing which is maximasing the engine performances. These 2-stroke kart engines can run in excess of 19,000 rpm. They can be both water and air cooled.