How are the Rotax 125cc two-stroke kart engines different from regular go-karts?

Most of us know that the foundation for F1 or any kind of single seat Formula racing is karting. That’s how Max Verstappen, Lewis Hamilton, and most F1 racers have started. And karting sounds pretty easy, right? It’s not. These aren’t the four-stroke go-karts that you drive for fun with friends on the weekend, these are race karts. Serious business. We were invited by Birel Art India, a racing team, to try out their race karts on a race weekend. Keep reading to know what these race karts really feel like.

Rotax 125 Senior Max Evo engine

The National Karting Championship in India is powered by Rotax engines, which is why this is also known as the Rotax Series. The RMC championship is very well-known globally and in India, with Rotax supplying their kart engines all over the world.

The Rotax 125 Senior Max Evo engine is a 125cc two-stroke engine that makes 30bhp @11,500rpm and 21Nm @9,000rpm. A two-stroke engine works differently from the four-stroke engines that you can find in the traditional leisure go-karts. In a two-stroke engine, the power cycle is completed in two piston movements (one up and one down) per crankshaft rotation, while a 4-stroke engine takes four movements (two up and two down) across two rotations. In layman terms, two-stroke engines fire once every rotation, while four-stroke fires once every two rotations. These engines also get a power valve, which opens up for more air at a certain rpm and gives you a strong boost. It almost feels like unlocking a new level of power and it is very audible. Given that it is a two-stroke engine, power is only available after 2000rpm. Before that, it is basically dead. If you slide the kart on the track, you will not stay in the power band anymore, and thus lose a lot of time on the track. Gradually leaning into the throttle pedal is always better here rather than just mashing it completely, because that’s how the kart and engine is set up.

All of this enables the kart to reach top speeds of around 120kmph or more. A better way of determining this is to take it on a kart dyno, a facility that only Birel Art India currently owns in Bangalore. At the Meco Kartopia circuit, these karts reach 100kmph on the main straight. Two-stroke engines are high-compression engines and therefore very high maintenance. It’s easy for these engines to seize, and rebuilding will cost ₹1.5 lakh, while buying an entirely new engine costs ₹5 lakh. Most racers in the National Karting Championship have been in the sport for many years, and buy new engines every year. A new engine is the only way to make sure the engine performs at its best. In fact, they go the length of buying up to three engines – one for the race, one for practice, and one as a spare.

Birel Art India karts

Birel Art is an Italian company founded in 1958 that produces karts, and is based in Lissone, Italy. Today, it’s one of the main players in the international karting scene. Birel Art India in collaboration with Deepak Chinappa and Arjun Gurudev of Evotron Motorsports are running this team, and recently invited us to try out their karts and participate in a race weekend.

The karts have a 1040mm wheelbase, and a steel frame. There’s about 1-inch (25.4mm) ground clearance and no suspension, which means you can feel everything. There’s immense lateral grip on offer, and you can really push these karts on the track. A kart chassis costs around ₹7 lakh, and because it is not always repairable, racers do tend to store a spare one. Chassis bending is very common in racing whenever you get into an accident or get pushed out of the track at a higher speed.

I participated in the RMC National Karting Championship Round 4 with Birel Art India to find out what really goes into racing. A lot more on this coming soon, stay tuned!