1981 Benelli SEI 6-cylinder
6-cyl. 900cc/80hp NA
With an experienced team and a lot of data.
Alejandro de Tomaso was an ambitious Argentinian, born into cattle money, who left for Italy at age 27 in 1955. He settled in Modena, got a job driving for Maserati and OSCA, and married American heiress Isabelle Haskell.
With some help from his wife’s financing, de Tomaso started building cars under his own name in 1959. He built a series of mid-engine DeTomaso sports cars through the 1960s, including the Vallelunga, Mangusta and Pantera. Not satisfied with just building automobiles, De Tomaso also acquired control of motorcycle manufacturers Moto Guzzi and Benelli in the early 1970s.
In 1974 de Tomaso announced the 748 cc Benelli Sei. It was the first six-cylinder bike to be seriously produced and was followed in 1979 by the 1,081 cc Honda CBX and the even bigger Kawasaki KZ1300. While the latter two were DOHC engines, the Benelli (which de Tomaso actually wanted to call a Moto Guzzi) was essentially a reverse-engineered Honda SOHC 550 cc Four with two more cylinders. It also had three Dell’Orto carburetors and a five-speed gearbox.
Just the mention of a motorcycle with six cylinders sounds pretty exotic and one would assume performance would be blistering. With the Benelli, though, this wasn’t quite the case. The Sei weighed a hefty 562 lbs, power output was modest at 71 bhp and top speed was only about 115 mph. Even so, the engine was only two inches wider than Honda’s 750cc four-cylinder since the alternator was behind the cylinders, which were separated for better cooling. The Sei’s angular lines were styled by Ghia, which de Tomaso also owned, and it copied Craig Vetter’s radical 1973 Triumph Hurricane with a fan of three trumpet silencers, although on the Benelli there was one on each side.
The cachet of being the only six-cylinder bike in production, and the reliability of the Honda-derived motor with its signature exhaust note, meant that sales were steady, with 3,200 units built by 1979. Testers praised the Sei’s maneuvrability despite its size, and the dual front disc brakes were effective.
In 1979 Honda launched the CBX, so Benelli increased the Sei to 906 cc, although sadly it was reduced to just two silencers and lost its exhaust song. The Sei inherited the bikini fairing from the Moto Guzzi Le Mans and and a later Sport model was fitted with a larger one later. In all, fewer than 2,000 of the 906 cc Sei models were sold, at a hefty $3,995 MSRP. The last was sold in 1984.
A substantial number of Benelli Seis survive, partly due to their exotic nature and consequent collectability, but also due to the ephemeral nature of any dealer support in the U.S. The difficulty of finding parts and service has meant that even the most enthusiastic rider carried prudence as a pillion passenger, and low-mileage examples are not uncommon.