Benelli 750Sei

Benelli 750Sei
Manufacturer	Benelli
Production	1974-75
Engine	Transverse six cylinders, four stroke, SOHC, 2 valve per cylinder
Compression ratio	9.8:1
Top Speed	190 km/h / 118 mph
Ignition	Battery ignition (later model electronic ignition)
Transmission	5 Speed
Suspension	Front: Marzocchi telescopic cartridge-type suspension forks (Some models used Paoli!) Rear: Dual Sebac shocks, preload adjustable
Brakes	Front: 2 x 300 mm discs, 2 piston calipers Rear: 200 mm drum
Front Tire	3.25-18
Rear Tire	4.10-18
Weight	220 kg / 485 lbs (dry),
Fuel Capacity	23 Liters / 6.1 US gal
Manuals	Service Manual

It could reach a top speed of 190 km/h / 118 mph.

Engine

The engine was a Air cooled cooled Transverse six cylinders, four stroke, SOHC, 2 valve per cylinder. The engine featured a 9.8:1 compression ratio.

Chassis

It came with a 3.25-18 front tire and a 4.10-18 rear tire. Stopping was achieved via 2 x 300 mm discs, 2 piston calipers in the front and a 200 mm drum in the rear. The front suspension was a Marzocchi telescopic cartridge-type suspension forks (Some models used Paoli!) while the rear was equipped with a Dual Sebac shocks, preload adjustable. The 750Sei was fitted with a 23 Liters / 6.1 US gal fuel tank. The bike weighed just 220 kg / 485 lbs.

Photos

Overview

Benelli 750 Sei

Benelli's exotic six-cylinder superbike deserves a place in any history of fast motorcycles, despite one undeniable fact: by the standards of mid-1970s superbikes. It wasn't outstandingly fast. The Italian machine was undeniably stylish, sophisticated and expensive but lacked the outright speed of the best Japanese superbikes and its Italian rivals alike. Despite this the Sei was a fine all-round performer, combining effortless acceleration, remarkable smoothness and excellent handling in an eye-catching package topped by six gleaming chrome-plated exhaust mufflers. As well as being the only six-cylinder bike on the market when it was launched in 1974. The Sei also came with a pedigree. Benelli. Based at Pcsaro on Italy's Adriatic coast, had won the 250cc world championship as recently as 1969, beating the two-strokes with a four-cylinder four-stroke ridden by Australian Kel Carruthers.

Inspired by Honda

Apart from its number of cylinders, the Sei's 748cc engine contained little innovative engineering, and was not outstandingly powerful despite a claimed peak output of 71 bhp at 8500rpm. Cynics commented that the SOHC unit was little more than one-and-a-half Honda CB500 motors. Like Honda's four it featured cylinder dimensions of 56 x 50.6 mm and a central camchain. Similar details such as the ribbed oil filter housing also revealed the main inspiration of the Italian firm's engineers.  But the Benelli motor also incorporated differences including its alternator, which sat not at the end of the crankshaft but behind the cylinders on the right, where it was driven by gears. That allowed the six-cylinder motor's crankcases to be narrow, as did the use of only three 24mm Dell'Orto carburettors, the outer two of which fed angled inlet manifolds that allowed the carbs to be close together beneath the fuel tank. The motor was tuned for mid-range performance and was impressively tractable, producing useful torque everywhere above 2000rpm in top gear. Carburetion was crisp, and there was barely a step in the power delivery as the revs rose through the range. This meant that although the Benclli's top speed of about 115mph (185km/h) was unexceptional, the bike impressed with its effortless high-speed cruising ability.  Rapid riding was also boosted by a chassis that was conventional in layout but which worked much better than most contemporary set-ups.

The steel twin-cradle frame held Marzocchi forks, plus rear shocks either from the same firm or Sebac. Both ends were fairly firm in Italian sporting tradition. In combination with the reasonably rigid frame, that helped give good straight-line stability.  For a big bike the Benelli was also impressively agile, and could be cornered faster than many much smaller machines. It had fairly generous ground clearance, especially considering its engine layout. Powerful twin Brembo front disc brakes, backed up by a rear drum, added to the six-cylinder machine's impressive chassis performance.  Sadly for Benelli and particularly the firm's boss, Argentinean car baron Alejandro de Tomaso, the Sei was not a sales hit. Despite its array of cylinders the Benelli lacked the character and performance that made the best rival Italian superbikes popular. Potential owners were worried about reliability and high running costs as well as the bike's considerable purchase price. The Sei nevertheless remained in production with few changes until the end of the decade, when its engine was enlarged to produce the 900 Sei. This had a little extra power and a neat headlamp fairing, but no more charisma. It sold in similarly small numbers and marked the end. at least for the next quarter century, of Benelli's attempt to become a major superbike manufacturer.

Source of review : Fast Bikes by Roland Brown

Make Model	Benelli 750 Sei
Year	1974-75
Engine Type	Transverse six cylinders, four stroke, SOHC, 2 valve per cylinder
Displacement	748 cc / 46.6 cu in
Bore X Stroke	56 x 50.6 mm
Compression	9.8:1
Cooling System	Air cooled
Exhaust	2 x 3-into-1-into-3
Induction	3 x 24mm Dell'Orto carburetors
Ignition	Battery ignition (later model electronic ignition)
Starting	Electric & kick start
Max Power	52.9 kW / 71 hp @ 8500 rpm
Transmission	5 Speed
Final Drive	Chain
Front Suspension	Marzocchi telescopic cartridge-type suspension forks (Some models used Paoli!)
Rear Suspension	Dual Sebac shocks, preload adjustable
Front Brakes	2 x 300 mm discs, 2 piston calipers
Rear Brakes	200 mm drum
Front Tire	3.25-18
Rear Tire	4.10-18
Dry Weight	220 kg / 485 lbs
Fuel Capacity	23 Liters / 6.1 US gal
Consumption Average	5.9 L/100 km / 17 km/l / 40 mpg
Standing ¼ Mile	14.0 sec / 148 km/h / 92 mph
Top Speed	190 km/h / 118 mph
Reviews	benellimotoclub - sei vs cbx vs z1300

External Links

• http://www.benellimotoclub.com/contenidos/iprudinonmc.htm
• http://www.benellimotoclub.com/contenidos/ipruseinmc.htm