The Benelli 750 Sei was the first production motorcycle with a six-cylinder engine. Masterminded by Alejandro de Tomaso in the early 1970s, it used an engine based on the Honda CB500 four with two extra cylinders, made 76 hp and was later enlarged to 900 cc.
Benelli 750 Sei at a glance
| Maker | Benelli, Pesaro; engines built at Moto Guzzi, Mandello del Lario |
|---|---|
| Production | 1974–1986 (English sources say 1973–1989) |
| Models | 750 Sei and 900 Sei |
| Engine | six-cylinder in-line OHC, air-cooled |
| Claimed power | 76 hp at 9,000 rpm (750 Sei) |
| Top speed | about 204 km/h |
| Carburettors | three Dell’Orto VHB 24 mm |
| Exhausts | six mufflers on the 750; six-into-two on the 900 |
| Design | Ghia (Paolo Martin) |
| Price at launch | 2,550,000 lire on the road |
| 750 Sei sales by 1979 | 3,200 |
| 900 Sei production | fewer than 2,000 over four model releases |
Sources differ on the production years: English Wikipedia gives 1973–1989, the Italian article 1974–1986.
History of the Benelli 750 Sei
De Tomaso’s six
At the beginning of the 1970s Alejandro de Tomaso took over Moto Guzzi and Benelli, two historic Italian brands weakened by Japanese competition. His plan was to copy the best Japanese models and improve on them. For the four-stroke multi-cylinders the engineers were told to take inspiration from Honda’s Four range, and the design was entrusted to Paolo Martin of Ghia, with Pirelli, Brembo and Marzocchi involved in tyres, disc brakes and forks. It was for this project that Brembo made its first motorcycle disc brakes.
Piero Prampolini, who had designed Benelli’s four-cylinder racers, was given the task of designing a 750 cc engine split equally between six forward-facing cylinders. The 750 Sei was presented at the end of 1972, causing a sensation, although the motorcycle was not yet ready for production and sales. The engine was based on the Honda CB500 four with two extra cylinders; the cylinder-head fins were squared off for a distinctive look, the alternator was moved behind the cylinders to keep the engine narrow, and air passages between the cylinders improved cooling. Three Dell’Orto VHB 24 mm carburettors fed the six cylinders, and the exhaust ended in six mufflers.
Production and the 900
Production began in 1974, with engines assembled at Moto Guzzi’s Mandello del Lario works and frames and assembly at Pesaro. The bike was heavy and looked cumbersome, yet reviewers found it handled surprisingly well, and it was one of the smoothest European tourers. Early reliability suffered from problems with the distribution and gearbox, blamed on the use of leaded steel for the shift forks and on cheap chrome plating of the rockers; the price of 2,550,000 lire on the road and the prestige of owning the only six-cylinder in production helped sales. By 1979 Benelli had sold 3,200 of the 750.
In 1979 the 750 was developed into the 900 Sei by increasing bore and stroke. It had six-into-two exhausts and a small bikini fairing taken from the Moto Guzzi Le Mans; fewer than 2,000 were made over four model releases, and it was later offered as the Sei Sport with a larger fairing. The Sei remained the only six-cylinder motorcycle in production until the Honda CBX arrived in 1978. Production ended in the mid-1980s, with the Italian article giving 1986 and the English one 1989 as the final year.
Design and features
- First production six: the 750 Sei beat every other manufacturer to a six-cylinder road bike.
- Honda-derived engine: a CB500 four with two extra cylinders and squared-off fins.
- Narrow packaging: alternator behind the cylinders and air passages between them.
- Ghia styling: angular bodywork by Paolo Martin, a break from traditional round shapes.
- Six mufflers: a distinctive exhaust note on the 750.
Benelli 750 Sei versions
- 750 Sei (1974–1979): 76 hp, 204 km/h, six mufflers.
- 900 Sei (1979–1980s): larger engine, six-into-two exhausts, Le Mans bikini fairing.
- 900 Sei Sport: later version with a larger fairing.
The six-cylinder engine was related to the four-cylinder 500 Quattro, and Benelli’s earlier big twin is described in the 650 Tornado article. More Benelli models are in the Benelli collection.
Video: Benelli 900 Sei / 6 Zylinder Sound vs ZZ Top
Video on YouTube.
Sources
- Benelli Sei, English Wikipedia: models, engine, performance, sales
- Benelli Sei, Italian Wikipedia: development, production problems, price
