On the move: Keller-Gilera dohc
A private citizen, the Swiss Jakob Keller, increased the potential of the Gilera Saturno San Remo considerably with a double-cam cylinder head and thus made history.
Motorsport is his great passion – regardless of whether it is racing cars or motorcycles. The Swiss Jakob Keller recognized the potential in the mighty single-cylinder engines of the Italian Gileras, the concept of which goes back to the years before the Second World War. When they first raced in San Remo in 1947, Carlo Bandirola and Oscar Clemencigh achieved a double victory on the Gilera racing machines derived from the series Saturno and impressively underlined that Gilera was quite capable of defying the dominant Moto Guzzi racers Offer.
To honor the racing successes, the new Saturno Competizione models were given the sonorous name “San Remo”. Thanks to the low weight, the extraordinary handiness and the good pulling power of the ohv motor already from the lower speed range, the San Remo is particularly suitable for races on narrow and winding roads. Even when the first four-cylinder Gilera were used in 1948, you can still see Italy’s top drivers Nello Pagani, Umberto Masetti, Libero Liberati and Carlo Bandirola occasionally in the singles.
Somehow, Keller manages to pull one of these San Remo racing machines ashore. It is clear to the Swiss who runs a car workshop with a filling station in Zurich that the potential of this engine is far from being exhausted. He needs more speed, but that can’t be achieved with the push rod engine despite the lighter valve train and reinforced valve springs. Only the conversion to an overhead camshaft, which eliminates the need for tappets and bumpers, would allow higher speeds. It would be even more effective to place two camshafts in the cylinder head based on the model of the twin-cam four-cylinder, i.e. to convert the ohv engine into a dohc engine.
Although it is easier to implement a drive using a control chain, Keller opts for gear wheels. He retained the crankcase, crankshaft and cylinder, and mounted a T-shaped gear housing on the right-hand side of the engine. The cascade consists of 7 straight-toothed gears plus the two on the camshafts. Each gear wheel has ball bearings, the lowest one drives the self-designed oil pump via another wheel on the same shaft. It is designed for a larger flow rate, has fine, milled and turned cooling fins and is flanged to the control housing from the outside.
The cams are custom-made by Jakob Keller with carefully crafted run-up ramps. This results in an amazing smoothness. The camshafts are stored in specially made light metal housings screwed onto the original cylinder head. In between there is a support that also holds the T-shaped control housing. The axis distances are fixed and ensure minimal tooth flank play. Setting plates directly on the valve stems adjust the valve clearance. The camshafts actuate the two valves via roller tappets. A 35 mm Dell’Orto SSI carburetor prepares the fuel / air mixture. The dohc engine weighs around 5 kilograms more than the ohv base, but the increase in performance more than makes up for the additional weight.
Last but not least, Keller donated a sidecar to his dohc-Gilera, and he soon got involved with his unique racing team. The performance of the engine not only attracts the attention of magazines such as DAS MOTORRAD or Die Motor Rundschau, which report on the great self-construction in 1950, 1951 and 1952. Even at Gilera in Arcore, northern Italy, one is mighty impressed: A staff of technicians and engineers work with enormous commitment on the development of complex four-cylinder engines, and a hobbyist named Keller shows them how a single-cylinder mobilizes almost the same performance. In fact, the one among all the factory machines is happily at the head of the field.
Keller and the Gilera factory
One day, the Swiss took note of a request from Gilera with great satisfaction. He is asked to be allowed to disassemble and measure his single-cylinder engine in the factory. It was not without pride that Keller agreed and in return received one of the famous four-cylinder racing engines. But this treasure does not find its way into the now orphaned San Remo team standing in the corner without a motor.
Keller constructs a new team; a vehicle that can actually be described as a racing car on three wheels, but which nevertheless precisely complies with the requirements of the international regulations for racing machines. This generally describes any motor-driven vehicle with fewer than 4 wheels as a motorcycle. Category A are solo machines with 2 wheels, Category B sidecars and so-called cycle cars – that is, three-wheeled vehicles with two steered front wheels, for example. Two seats, side by side or one behind the other, are required, as is a track width of at least 80 cm. And instead of a passenger, it is possible to use an additional weight of at least 60 kilograms.
Keller’s construction meets all of these criteria. In order to be able to bring the performance of the four-cylinder to the ground better, it even has an additional 107 on board instead of the 60 kilograms. With this tricycle he finally drives the completely baffled competition in the ground. The record of approx. 190 km / h set in Monza by the BMW works drivers Noll / Cron is surpassed by Keller with an incredible 208 km / h. Protests are hailing from all sides, but they are thrown down: after all, his cycle car complies with the rules. At the end of the race in Regensdorf, the protests culminated in a drivers’ strike.
And again it is a brilliant Swiss – this time Rolf Biland – who two decades later again caused a sensation with a racing team of a special design, shocked the competition and had to accept heaps of protests. Coincidence? Duplicity of events? Maybe both. At this point, Jakob Keller had long since hung up his helmet and racing overalls. His vehicles are sold; he only kept the single-cylinder engine and put it in a showcase at home. Most recently, the Gilera engine served as a power source for a self-made racing car after the Formula 500 was developed in automobile racing – a class for miniature racing cars, mostly powered by air-cooled half-liter motorcycle engines. Even with that, the Swiss was always good for a place in the top ranks.
After Jakob Keller‘s death in the 1970s, his engine was sold to a collector who installed it again in a San Remo chassis and restored it to perfection. In 2005 the motorcycle finally passed into the hands of its current owner, Jo Kaufmann. On the occasion of a special racing machine run by the Veteran Vehicle Association (VFV), he brings it to Hockenheim, where it can be used as a race for the first time in many years. This time not as a team, but as a solo machine. Here too, in the field of racing machines up to the 1970s, the Keller-Gilera is at the forefront. Six decades after its construction, it has not lost any of its performance and its captivating beauty.
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