Four to the fore

There are many different ways to make a motorcycle go fast, but today’s most popular engine configurations are the inline four, the V4 and the vee-twin. There’s no doubt which is most common.

Most medium-to-large-capacity Japanese bikes use inline fours, including Yamaha’s hugely successful YZR-M1 MotoGP machine. The first so-called superbike, Honda’s CB750 of 1969, also used an inline four, thus many people assume the layout is a product of the Japanese mind. But it isn’t.

This particular engine architecture is 90 years old, a product of early 20th century Italian minds, possibly breathing the spirit of the Futurist movement that had taken Italy by storm in the years leading up to the Great War.

When Roman engineering graduates Piero Remor and Carlo Gianini built their inline four in 1923, the concept of using four smaller pistons instead of one thumping great piston wasn’t entirely new. What was new was their decision to arrange the cylinders across the engine instead of in line astern, which inevitably created cooling problems, as well as demanding an over-long wheelbase. Yamaha still cites the M1’s short wheelbase as a major advantage of the inline-four layout.

Remor and Gianini were building the future of motorcycling but the world didn’t seem to care. They struggled to attract backing and nearly went under before sporting aristocrats Count Bonmartini and Prince Lancellotti (no, really) injected some money.

During 1933 the engine was entirely redesigned in Bonmartini’s Compagnia Nazionale Aeronautica aircraft factory outside Rome. What had started out as an air-cooled, single overhead-cam 500cc four, making a modest 28bhp, was now a water-cooled, supercharged, dohc monster producing 86.

Now assisted by brilliant engineer/rider Piero Taruffi, they got their engine so right that its layout is recognisable in Rossi’s M1: forward-inclined cylinders, central gear cam drive, wet sump and so on.

Bonmartini christened his new motorcycle the Rondine, after the plane that had accompanied Mussolini during his march on
Rome that brought the dictator to power in 1922. The Rondine’s first race was a walkover – the bike utterly defeated the Moto Guzzis in the 1935 GP of Tripoli, in Italian colony Libya.

Bonmartini then lost interest in the project, which was bought by Guiseppe Gilera, founder of the eponymous motorcycle marque. In 1937 Taruffi manhandled the streamlined four to 170.37mph on the Brescia to Bergamo autostrada, smashing the 500cc and 1000cc world speed records.

Weeks before the outbreak of WWII , Dorino Serafini won the 1939 European title on the Gilera, defeating favourite Georg Meier and his supercharged BMW . Mussolini must have been happy; like Hitler, he was keen to use motor racing successes to boost national pride.

After the war, supercharging was banned from the sport’s new World Championships, so Remor built an air-cooled inline four, which won five of the first seven 500 world titles. After falling out with Gilera, Remor defected to the nascent MV Agusta. Inevitably the first MV four was little more than a Gilera clone.

MV began its legendary series of 500 GP successes with Remor’s four, and when Honda entered the premier class in 1966, its RC181 wasn’t dissimilar. On the roads, Honda’s CB750 was followed by Kawasaki’s Z1 and other fours from Suzuki and Yamaha. No wonder this type of machine became known as the UJM – the Universal Japanese Motorcycle – but its seeds were sown in Rome, not Tokyo.

Mat Oxley