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Digital Subscriptions > Vroom International > n. 211 January 2019 > Double … or nothing!

Double … or nothing!

The twin-cylinder engine used to be a great protagonist of the gearbox categories from the very origins of karting to 1987, when it was banned for a series of not entirely clear reasons. The best specimens, in 1987, delivered nearly 50 HP. Today, they’d be putting out 65, versus the KZ’s 45 HP.

We begin to tell this story from the end. When one talks about horsepower there are people in the pits who really lose their sense of measure, or proportion, sometimes triggering a war to the last HP that leads to an escalation that is nothing short of ridiculous. And then you hear about 50 hp for a single cylinder KZ with 30 mm carburetor, fixed advance ignition, compression limitation and 10,000 regulatory issues. To put everyone back in line, we’d like to begin by saying that the best 125 single cylinder ever built, that is the Aprilia RSA of the Maestro Jah Thiel, delivered 54 hp in its most “extreme” version, the engine that won at its debut with Mattia Pasini and that was never again seen on track for its manifestly demonstrated superiority. The cylinder and the crankshaft of that motorbike were no longer used. In light of this - and today I feel fine and generous – the 45 hp of the current 125 KZ start to make more sense, if one considers that the powerful Aprilia used quality gasoline, programmable ignitions, 43 mm carburetor and superlative compression ratios. Precisely for this reason we can understand why the 50 hp of the two-cylinder Garelli, always by the good Jan Thiel, were legend in 1987, against about 40 of the best official single-cylinders which raced in the 1988 MotoGP (like the Derbi of Jorge Martinez, winner of the first world for single cylinder). Karting has always been just short of the HP developed by motorcycle engines not for obvious technical inferiority, but for the need to have greater torque at low speeds required to push a lot of sticky rubber glued to the ground at the starts. The engines of the world motorcycle championship, in fact, in Formula C have always been badly beaten, to say the least. So imagine today what a single-cylinder with 52 hp (real) or a 65 hp two-cylinder engine on a kart could be! It should be remembered, in fact, that the advantage of the twin-cylinder is given by a 15% increase in capacity compared to the single cylinder, in addition to an advantage guaranteed by mechanical fractioning. Fact is, in 1987 the twin cylinders were banned from international karting a year earlier than in the world motorbike championship. The main excuse was that they wanted to stay in touch with the world of motorcycles and involve their manufacturers; others said that the twin cylinders were too powerful and dangerous. In practice, two shameful lies. First, the motorcycle engines, as mentioned, have never worked on karts for a matter of delivering power - the motorbike has a 1 cm rubber footprint on the ground and is always with the high gears in; karts are the complete opposite; second, remember when Vincenzo Sospiri won the Italian Formula C at Magione (bear in mind the straight of Magione) with a single- cylinder Pavesi trimming 10 seconds off the best twin-cylinder (Mazzola’s Balen), meaning what – that the single cylinder was also dangerous, since it was even faster when the chassis (and the rider) were especially on top of their game? Moral of the story: they lost extraordinary engines and a generation of drivers who stopped running having to give up their engines.

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About Vroom International

In this issue: Brazil, one great debut! Rotax bets on Brazil for the 2018 Grand Finals and wins, creates an unforgettable event! ENGINES HOMOLOGATION 2019-2021 Tm, Iame, Modena Engines, Vortex LEGENDARY KART LANDIA 1° KARTING EXPÒ IN ITALY, ONCE AGAIN! I Love kart PINK PASSION THE WAY WE WERE THE EPIC OF THE 125 TWIN-CYLINDER IN KARTING THE VIRTUAL WORLD - PART II Special What helmet do I wear?