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DUCATI 900 SS

Article #7, 10 April 2011 by Harné Heuvelman

In 1974 the 860 GT was introduced and the highly exotic 750 Super Sport ‘round case’ was in its final year of production. Although Ducati had no intention to bring another limited production race replica to the market, the bad market reception of the 860 GT made them think…

“What if we build a new Super Sport to show the world what we got? The new ‘square case engine can be used to prove we still have it” This must have been the buzz in Bologna in 1975 when development of the 750 and 900 Super Sport began in 1974. Another limited production race-derived model was about to appear.

The ’75 Ducati 900 SS used the same frame as the earlier 750 SS and shared its bodywork and chassis with the 750 SS of the same year. The only difference (apart from engine displacement of course) between the two is the colours of the fairing: where the 900 SS has a blue fairing with a silver stripe, the 750 SS has a silver fairing with a blue stripe. The Marzocchi 38mm front fork was retained but now fitted with a Brembo brake system.

The 1975 900 Super Sport was a fine display of what Ducati had to offer. Using the new 863cc ‘square case’ engine as a basis combined with the frame from the earlier 750 Super Sport ‘round case’, the 900 SS was – once again – a road legal racer.

Or was it? Because in the process of designing the bike, Ducati forgot all (US) regulations it had to comply with. The 900 SS had right side gear shift (where left was now obligatory) and with the 40mm Dell’Orto’s and Conti mufflers, the noise exceeded every government regulation.

It was clear for obvious reasons that Ducati had to ‘soften’ the concept in 1976. To comply with US regulations, the ’76 and ‘77 900 SS models got Lafranconi mufflers, air filters and left side gear-shift by adding a crossover rod and different foot pegs. The fuel tank was that of the previous 750 Sport and was made from steel rather than fibreglass.

In 1978 the Super Sport range got an engine update based on the new Darmah. It got a new crankshaft assembly, new Bosch ignition and gear selector drum on the left side; a big improvement over the crossover rod. Both solo and dual seats were now available.

The 1979 900 Super Sport was restyled and now came in black and gold colour scheme and, at first, with magnesium Speedline wheels soon to be replaced by aluminium FPS wheels in the same year.

Further, final updates took place in 1981 when the 900 SS received a mild engine update and another redesign. The bodywork was now silver painted with new decals, combined with a black painted frame. A dual seat was now standard, but came with a removable seat pad. By 1982 the 900 SS, in production since 1975, was seen as an old-fashioned bike. The model was discontinued after 1982.

The 900 SS was replaced by the 900 S2 in 1982. An electric starter motor was introduced as an optional extra, sharing its engine specifications with the Mike Hailwood Replica Mk4. The frame was also shared with the later Mike Hailwood Replica models and had the same kinked rear down tubes troubling the handling. In 1984, together with the Mille Mike Hailwood Replica the 900 S2 was replaced by the Mille S2, again sharing specifications with its brother.

With the development of the Pantah engine, the bevel drive era that was started with the 100 Gran Sport in 1955, with many racing victories and superb road bikes as the 750 SS and 900 SS, finally came to an end in 1986.

Engine

The 863cc ‘square case’ L-twin was introduced on the 860 GT and formed the basis for all other ‘square case’ models introduced later on. Although technically based on the 750 ‘round case’ L-twin, this engine had a lot of improvements for faster and simpler assembly. The outer engine cases were designed by Giorgetto Guigiaro of Studio Italdesign. The engine has vertically split aluminium crankcases, a 90 degree L-twin layout with the vertical cylinder inclined at 15 degrees upwards.

The 900 SS received the desmodromic cylinder heads of the ’74 750 SS as well as the 40mm Dell’Orto PHM carburetors and the Conti exhaust mufflers. The engine update for 1976 included a left side gear-shift via a crossover rod. The 1978 750 Super Sport has an updated crankshaft, Bosch ignition and an updated gear shift mechanism. The 900 S2 electric start shares its specifications with the Mike Hailwood Replica Mk4 and featured Gilnisil coated cylinders and a dry hydraulic actuated clutch. 

Frame

The frame for all 900 Super Sport models is based on that of the 1973 750 Sport with the ‘narrow’ rear sub frame. With the introduction of left side gear shift in 1976 came revised foot pegs and different positioning of the rear brake pump. The 900 Super Sport is fitted with a 38mm centre axle Marzocchi front fork and dual Brembo 280mm disc front brakes and a single Brembo 229mm disc brake at the rear.  The ’74 and ’75 models had a fibreglass fuel tank, replaced by a steel fuel tank (the same as the 750 Sport) in 1976. Until 1978 all 900 Super Sports were fitted with Borrani aluminium wheels, later replaced by either magnesium Speedline or aluminium FPS six spoke wheels.

References (recommended further reading)

Falloon, Ian (2004) Standard Catalog of Ducati Motorcycles, Iola: KP Books

Falloon, Ian (2008) ‘The Ducati Bible: 860, 900 & Mille All models 1975 to 1986, Dorchester; Veloce Publishing

Falloon, Ian (1998) ‘Ducati Twins Restoration Guide, Bevel Drive 1971 – 1985, Osceola; MBI Publishing Company

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