4 Stroke Racing

Kart racing in the UK is divided into two main categories: 2-stroke racing and 4-stroke racing. Within these two engine categories, there are further sub-divisions (which are known as karting classes). The direct drive classes can use either 2-stroke or 4-stroke engines, while the gearbox classes use engines that are mostly of the 2-stroke variety. This article focuses on 4-stroke karting, but we have a separate article on 2-stroke karting.

What are 4-stroke engines?

4-stroke engines are often industrial, air-cooled engines (unlike 2-stroke engines, which are mostly water-cooled) that have been slightly altered to fit into a kart. Honda are one of the main manufacturers of these type of engines, but these aren't specifically designed for karting purposes, so they are best suited to those who want to kart for fun or only on a semi-regular basis. Yamaha and TKM produce more powerful types of 4-stroke engines for those who are more serious about karting. These are produced specifically for karting and can run to 11,000 rpm (revs per minute). Many of these are used in the National Championship karting classes.

Karting Classes That Use 4-Stroke Engines

There are several karting classes in the UK that use karts with 4-stroke engines. Some of the karting classes are briefly outlined below, but see our two articles on Junior and Senior karting classes for more information on them.

• Honda Cadet: This is a junior karting class that uses a Honda Gx160 160cc engine with clutch. Children aged eight to twelve are eligible for the class.
• Junior TKM - 4S: This is a junior karting class that uses a TKM 200 c 4-stroke junior engine with clutch and restrictor. Children aged eleven to sixteen are eligible for the class.
• Honda Junior Heavy: This is a junior karting class that uses a Honda Gx160 4-stroke engine with clutch. Children aged eleven to sixteen are eligible for the class.
• Formula TKM - 4S: This is a senior karting class that uses a TKM 200 c 4-stroke engine with clutch. Children over sixteen are eligible.
• Honda Senior: This is a senior karting class that uses Honda Gx160 160cc 4-stroke engines with clutch. As with all senior karting classes, anyone over the age of sixteen is eligible to race in the class.

4-stroke engines are used in more than a few karting classes in the UK, but they aren't as commonly used as 2-stroke engines, which feature in the vast majority of karting classes in the UK. As a kart driver, it doesn't really matter which engine your kart is using, as you're not required to alter your driving style according to whether your kart has a 2-stroke or 4-stroke engine. The main difference is the power. 4-stroke engines can range from 5 to 20 hp (horsepower), while 2-stroke engines tend to have a hp of between 4 and 7 for a single cylinder 60cc engine (a 2-stroke twin 250cc engine can reach up to 90 hp, but most karting classes in the UK don't use engines that are this powerful – most are around 160cc or less).