Bimota SB2
With Phil Aynsley
Bimota achieved considerable success with their competition designs (the 1972 HB1, Jonny Cecotto’s 1975 World Championship winning 350 Yamaha and the 1976 250 and 350 Aermacchi-Harley Davidsons of Walter Villa), and debuted their first street motorcycle in 1976.
The design was commissioned by the Italian Suzuki importer SAIAD following on from their earlier order for a Bimota chassis to house a TR500 motor (the SB1). The only stipulation was that the GS750 engine had to be used.
Massimo Tamburini was determined to advance the state of the art for sporting road bikes so his SB2 design featured such items as a perimeter frame, mono shock rear suspension and adjustable steering angle.
The chrome-moly steel frame directly connected the steering head to the swingarm pivot point and employed the motor as a stressed member of the chassis.
The frame was built in front and rear sections that were mated with conical joints. It weighed just 10 kg. A major feature of the swingarm was that it pivoted concentrically with the countershaft sprocket, ensuring constant chain tension.
The original design had the exhausts exiting from under the seat (as per his much later Ducati 916 design) and the fuel tank located under the motor.
Both these ideas proved too hard to execute for a production motorcycle so the alloy and fibreglass monocoque seat unit’s exhaust exit points were used to house the rear indicators.
The SB2 was available in three options: a kit, a complete bike and with a Yoshimura 850 cc hot-up kit fitted. 140 frames/kits/bikes were built between 1977-80.
The bike seen here is one of the first 90 with the next 30 using simpler bodywork that resembled the KB2’s (these were designated the SB2 80). The remaining frames were destroyed after the supply of GS750 motor was stopped.
In ‘standard’ form the SB2 made about 60 hp and weighed 196 kg dry – some 30 kg less than the Suzuki GS750.
The Yoshimura kitted SB2s featured over-bored cylinders, Road & Track camshafts, race valve springs, 69 mm high compression pistons and 29 mm Mikuni Supercarbs. It was dyno tested at 78 hp at 9000 rpm.
Bimota SB2 Specifications
| Bimota SB2 Specifications | |
| Engine | Air-cooled, tranverse four-cylinder, four-stroke, 743 cc |
| Bore x Stroke | 69 x 56.4 mm |
| Compression Ratio | 10.5:1 |
| Induction | Dual 29 mm Mikuni carbs |
| Max Power | 75 hp @ 8700 rpm |
| Max Torque | 56.9 Nm @ 8250 rpm |
| Gearbox | Five-speed |
| Frame | Chome molybdenum steel |
| Suspension | 35 mm Ceriani telescopic fork, Corte & Cosso monoshock, preload adjustable |
| Brakes | Dual 280 mm front disc brakes, single 260 mm rear disc brake |
| Weight (Dry) | 196 kg |
