When visiting premier custom workshops, you expect to encounter impressive builds, hand-shaped sheet metal, and meticulously restored classics. However, during a recent trip to Gasoline Motor Co. in Waterloo, Sydney, I had the privilege of standing inches away from a genuine holy grail of classic Italian motorcycle engineering: a original 1975 Ducati 900 Super Sport “Square Case”.
While many enthusiasts revere the famous 1974 “Greenframe” 750SS (of which 401 units were made), fewer realize that the first-year 1975 900SS is actually significantly rarer. Ducati produced a mere 246 units of the 1975 900 Super Sport globally, with only 99 officially imported into Australia.
Here is the story behind this legendary machine, what the crew at Gasoline Motor Co. shared about its mechanical quirks, and why this specific model holds such a revered place in motorcycle history.
From Imola to “Square Case”: The Origin Story
To appreciate the 1975 Ducati 900SS, one must understand where it came from. In 1972, legendary British racer Paul Smart and teammate Bruno Spaggiari dominated the Imola 200 on Fabio Taglioni’s newly engineered 750cc 90° L-twin with Desmodromic valve control. That victory transformed Ducati overnight from a small-displacement manufacturer into a global superbike powerhouse.
The production version of that race bike became the 1974 750SS “Round Case”, so named because of the smooth, rounded engine crankcases.
By 1975, Ducati updated the crankcase design to a more angular shape penned by automobile designer Giorgetto Giugiaro (originally for the 860GT line). Thus, the “Square Case” bevel-drive engine was born. While the 860GT touring models struggled commercially, Taglioni took that expanded 864cc square-case motor, fitted it with high-compression pistons, aggressive Desmo camshafts, and huge 40mm Dell’Orto carburettors, and dropped it into a minimalist chassis: the 1975 Ducati 900 Super Sport.
Workshop Insights from Gasoline Motor Co.
Talking with the technicians at Gasoline Motor Co. while inspecting the bike offered a masterclass in 1970s race-homologation details. Unlike later, more civilized iterations of the 900SS, the 1975 model was essentially a road-legal factory race bike built with very few compromises:
- Right-Hand Gear Shift: The 1975 model was the final year before US Department of Transportation mandates forced European manufacturers to standardize on a left-hand gear shift with a 1-down, 4-up pattern. The ’75 900SS features a traditional right-foot gear lever operating a 1-up, 4-down pattern.
- Unfiltered Dell’Orto Carburettors: The twin 40mm Dell’Orto PHM carburettors came directly from the factory fitted with open velocity stacks and wire mesh screens, no air filter boxes restricting air intake.
- Conti Exhaust Pipes: The iconic chrome Conti silencers produce a sharp, booming mechanical exhaust note unique to Taglioni’s 90° bevel-drive twins.
- Pure Mechanical Experience: There is no electric starter. Starting the high-compression 864cc twin requires a firm kick, precise choke lever adjustment, and respect for the kick-start lever’s return arc.
During my visit, I captured a close-up visual tour of this rare beast sitting on the shop floor:
Technical Specifications: 1975 Ducati 900SS
Data sourced from historical archives published by MCNews Australia and classic motorcycle documentation from Silodrome:
| Specification | Technical Detail |
| Engine Type | 864cc SOHC 2-valve per cylinder, Desmodromic 90° L-Twin |
| Bore x Stroke | 86.0 mm × 74.4 mm |
| Compression Ratio | 9.2:1 |
| Fuel Delivery | Dual Dell’Orto PHM 40mm carburettors with velocity stacks |
| Horsepower | Claimed 80 hp @ 7,500 rpm (~68 rear-wheel hp) |
| Torque | 57 ft-lbs (77 Nm) @ 6,500 rpm |
| Transmission | 5-speed manual, right-hand shift (1-up, 4-down) |
| Dry Weight | 188 kg (414 lbs) |
| Frame & Suspension | Tubular steel trellis frame, 38mm Marzocchi front forks, dual rear shocks |
| Braking System | Dual 280mm front Brembo discs, single 229mm rear disc |
| Top Speed | ~217 km/h (135 mph) |
| 1975 Production Volume | 246 units worldwide |
The Racing Pedigree: The Mike Hailwood Connection
The historical importance of the 1975 square-case engine extends straight into motorcycle racing lore.
In 1978, legendary 11-time World Champion Mike “The Bike” Hailwood came out of an 11-year Grand Prix retirement at age 38 to tackle the dangerous Isle of Man TT. Riding a heavily modified Ducati 900SS built by Manchester dealer Sports Motorcycles, built directly upon the square-case bevel-drive engine platform introduced in 1975, Hailwood shocked the racing world by defeating the dominant factory Honda team to claim victory in the Formula 1 TT race.
That win proved that Fabio Taglioni’s square-case L-twin was not just a beautiful piece of machinery, but a world-class race winner capable of defeating multi-cylinder Japanese competition.
Final Thoughts
Encountering a 1975 Ducati 900 Super Sport in person at Gasoline Motor Co. was a rare treat. In an era where modern superbikes rely on traction control, ABS, ride-by-wire throttles, and electronic suspension, standing next to a hand-built Italian homologation special with open carburetors, bevel gears, and raw mechanical energy is a reminder of motorcycle design at its purest.
With only 246 ever crafted, this 1975 Square Case remains an enduring testament to Ducati’s golden era of air-cooled racing heritage.
External References & Further Reading
- MCNews Australia: Ducati’s Iconic 1975 900 Super Sport History
- Silodrome: Ducati 900SS — A Thoroughbred Italian Superbike From The 1970s
- Gasoline Motor Co. Official Site
- Reize Productions YouTube Short: 1975 Ducati 900SS Encounter