Bianchi Twins

BIANCHI TWINS

Technical Analysis:

BIANCHI is the oldest Italian motorcycle factory, having been founded in 1885, and beginning production of motorized two-wheelers in their Milan factory at the turn of the century.

The firm has always taken an interest in sporting events, particularly Grand Prix racing in the 350cc and 500cc classes. For example, in the middle twenties Bianchi produced a 350cc double overhead camshaft bike which the legendary Tazio Nuvolari rode to many successes.

Ten years later a 500cc racing Bianchi. still of the single-cylinder, double knocker type, launched toward fame other riders, such as Alberto Ascari. Dorino Serafini and Giordano Aldrighetti. All of these men. but particularly Nuvoiari and Ascari, went on to become even more famous as drivers of racing cars.

Shortly before the outbreak of the second world war, the Bianchi racing department developed a supercharged 500cc “four.” This machine showed great promise during testing, but was not actually raced because hostilities temporarily halted international competition. After the war, regulations were changed to ban superchargers, and without its blower, the machine was no good. The engine itself, a marvelous example of the engineer’s art, can still be seen at the Bianchi factory.

In 1960, after many successes in Italian sports machine races and scrambles, with “derived from the series” models, Bianchi’s directors decided to again have a go at Grand Prix racing. Engineer Lino Tonti, head of their experimental and development department (and previously in charge of the Benelli and Mondial racing departments), was quick to produce a suitable machine: a dohc twin, with 55.0 x 52.5mm bore and stroke dimensions and a displacement of 248cc, producing 41 bhp at 12,000 rpm. Although this power output was very respectable, the engine/transmission unit proved to be too big and heavy, so it was decided to increase the bore to 65mm and run it in the 350cc class. The stroke remained unaltered, so the same crank, rods, etc., could be used.

In this 350cc form the machine was much more successful. Late versions have 9.8:1 compression ratio and are fed by a pair of 32mm GP-pattern Dellorto carburetors — and develop an impressive 53 bhp at 10,800 rpm. In the hands of Italian Champion Remo Venturi, a 350cc Bianchi won the 1963 Gold Cup at Iniola, defeating opposition of the highest caliber, including Derek Minter and John ITartle on Güera fours.

Wishing to compete in the 500cc class as well. Bianchi technicians under the direction of the talented Lino Tonti again “stretched” their engine. At first, a 380cc model was produced, to be eligible for 500cc-class events, by simply increasing the bore to 68mm. Of course, this was too little to make the engine competitive against the 500cc fours, so both bore and stroke were increased to 69mm x 56.2mm, which gave 440cc. Finally, by using all of the room inside existing cases, the bore was once again enlarged, to 70mm. and the stroke increased to 59.2mm. That gave 452cc; and in an engine that made its start in the 250cc class. The power from this remarkable Bianchi twin is 65 bhp at 10,000 rpm. The engine has the same compression ratio as the 350 model, but is fed by larger, 35mm carburetors.

In this latest stage, the Bianchi has to be a formidable rival for the best existing 500cc machines. In fact. Remo Venturi rode one to victory in the last 1963 Italian Championship event held at Sanremo. defeating Silvio Grassetti on the World Championship-winning MV four.

Both the 348cc and 452cc Bianchi racing bikes follow the same engine and frame layout, and there is only a slight difference in weight (282 lb. for the 350 and 297 lb. for the 500). The 350 uses 2.75-18 and 3.25-18 tires, front and rear: the 500’s tires are 3.00-18 and 3.50-18. Both machines have twin-drum, four-shoe brakes (similar to those of the G.P. Honda) at the front wheel, and a single-cam, two-shoe conventional-pattern brake at the rear.