The Legacy Of Fabio Taglioni And The Ducati Pantah 500

[Hugh Janus]

The Fabio Taglioni-designed Ducati Pantah SL 500 was the fastest bike in its class at the time. (Bruno dePrato Collection/)

Dr. Fabio Taglioni is principally—and rightfully—remembered for having designed the only desmodromic distribution train that proved so rational, reliable, and consistent, it became a regular production component of all Ducati engines. But I would also remember Dr. Taglioni for his spirit, his great ethics, and his deep moral honesty, and for great passion and dedication. You should have seen him at the drawing board, sketching perfectly neat lines that needed hardly any touch-ups because he had already configured the project in his mind, down to the last detail. Many portray Taglioni as a stubborn conservative, but none of them ever had the privilege of working under his lead. Sure he was “old school,” as were most of those involved in motorcycle engineering at the time, but he always put maximum effort into refining and evolving what was tried and true, and when he knew he’d extracted the ultimate potential of a given concept or technology, he was always open to investigating the latest innovations. Above all he was always available to discuss new concepts and solutions brought forth by his younger assistants. 

Fabio Taglioni and his magic pencil at work at the drawing board. (Bruno dePrato Collection/)

That’s how, around the mid-‘70s, Taglioni got around to confronting two major problems facing Ducati at the time. First, the new models had to put an end to the landslide of broken crank assemblies that were destroying Ducati’s reliability image. The fact is there was a total lack of quality control, since the press-fit crankshafts were never checked for correct alignment and duly squared off, leaving the production manager to waste lots of time and money recalculating every component and testing alternative solutions. Second was the need to give life to a new midsize 90-degree V-twin that could drive sales in that growing market. 

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The basic parameters of the project had taken shape back in 1972, during a meeting at the Ricardo R&D headquarters in London to discuss the effective solutions to the crankshaft problem. At the time, responsibilities of the production manager and quality control standards were vague, so the discussion went round in circles. Eventually, however, someone asked, “What if we switched from press-fit crankshafts on ball bearings and needle cages to solid forged crankshafts on plain bearings?” The Ricardo technicians agreed “that would be the ultimate solution,” but Taglioni roared back in protest, “Are you trying to rob my engines of their ultimate potential?” It was an understandable response; at that time in the industry, only the Moto Guzzi V7 transverse 90-degree V-twin and the Honda CB750 Four had forged solid crankshaft turning on plain bearings at all ends.

This original Ducati Pantah 500 V2 engine is kept in the Ducati Museum in Bologna, Italy. (Bruno dePrato Collection/)

Taglioni may have shut down the discussion then, but the incident lingered in the back of his mind. As Fabio pondered the design and structure of the crankshaft for his new 90-degree V-twin he realized the radical evolution that plain bearings and lubricants had gone through, especially in the USA, but also in Formula One and GT racing. Only Porsche was still building the first generation of its magic 356 Carrera 2.0-liter engine around a Hirth-type crankshaft, and by that point Taglioni was sold on the forged solid crankshaft concept. But he still did not want to completely turn the page, so for his new V-twin he selected the same proven MRC angular contact ball bearings used in the 750–900 SS for main bearings, reserving the plain bearings for the cap-type rods. Hybrid solutions like this were not uncommon at the time, especially on high-revving engines (another grand old man, Enzo Ferrari, fitted roller bearings at both ends of his supreme F1-racing V-12s). 

Dr. Gigi Mengoli is the only member of the original Taglioni team still active; here he’s seen with the original Pantah 500 V2 and its derivative, the present Scrambler 800 unit. (Bruno dePrato Collection/)

Main end journals were 35mm, the crank journal was 40mm, and the two combined to create, in the axial view, an 8.5mm overlap that would ensure an almost perfectly flex-free structure. Given the impossibility of feeding oil through the ball-type main bearings to support the rod’s plain bearings, the crankshaft left end was further supported by a bushing inserted in the left-side crankcase cover. The bushing was sealed to route pressurized oil from the pump to the duct inside the crankshaft. Axial feeding is a more positive way to feed oil to the crankshaft than through the radial orifices on the main journals because then oil flow has no centrifugal force to overcome. 

Taglioni was set on using the best European plain bearings at the time, British-made Vandervells, but someone suggested that American Clevite CL-112s were superior. And Clevite CL-112 it was. As always, the rods featured a center-to-center measurement that would return an above 2:1 ratio to the stroke to kill friction and secondary imbalance; in this case 124mm rods for a 2.14:1 ratio. 

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The crank assembly was just the most prominent sign of the new approach Taglioni adopted when designing the Pantah 500 90-degree V-twin. Bevel gears and related shafts were a very distinctive and elegant mark of the Ducati SOHC engine, in both the single and twin configurations. And Taglioni calculated the size and torsional rigidity of the shafts so that they could act as  torsion bar springs to smooth out the peak loads that aggressive cam profiles could generate through the valve drivetrain. As an example, the mighty Ford-Cosworth DFV 3.0-liter V-8 suffered from distribution gear train failures in early F1 Grand Prix outings because of excessive loads on the unyielding gear sprockets; the sprocket teeth disintegrated. But bevel gears were expensive and hard to keep at the right tolerance, and this new V-twin was supposed to be accessible in price and in ease of maintenance. 

The Pantah's adoption of toothed belts for the valve drivetrain was a brilliant solution to aggressive cam profiles. (Bruno dePrato Collection/)

Morse-type chains were utilized at first, but they also were expensive, so Taglioni turned to the fresh technology of toothed belts, which showed good promise. They were reliable, needed minimal maintenance, and would stretch less than chains yet yield that one-tenth of a whisker that would help smooth out distribution peak loads. And they were so quiet! As usual, Taglioni designed a pair of very elegantly shaped, polished aluminum belt covers to contribute a refined, finished look for the bike. Less noticeable was the adoption of Nikasil-coated cylinder bores to replace the traditional cast-iron liners, but the improvement was substantial: a cooler running engine and tighter piston-to-cylinder tolerances, yet less friction. 

Taglioni’s design for the original toothed cam belt covers was just one of the bike’s elegant details. (Bruno dePrato Collection/)

And there ends the list of innovative technologies Taglioni adopted for his new 90-degree V-twin, to both enhance its reliability as well as maintain its industry-leading edge. 

As for the thermodynamics, he simply extracted the best solutions from his enormous trove of experience. Bore and stroke were set at 74mm and 58mm, directly derived from the 74mm by 57mm of the 250cc SOHC single, and of the short-lived but promising 90-degree 500cc GP racer. The extra millimeter was added to reach the full displacement. The SOHC head featured a combustion chamber of very compact profile thanks to valves set at a 60-degree included angle, the result of a positive experience with the short-stroke 750cc racer that finished second only to Jarno Saarinen’s unbeatable Yamaha TZ350 at the 1973 Imola 200. The valves, a 37.5mm inlet and 33.5mm exhaust, were actuated by a refined desmodromic train, with no spring cams as an alternative. The combustion chamber was a real jewel of efficiency, with its high swirl turbulence generated by a generous squish band, in the best Taglioni tradition. 

The Pantah’s SOHC head featured a combustion chamber with valves set at a 60-degree included angle and an ample squish band, making for a very efficient two-valve motorcycle. (Bruno dePrato Collection/)

Compression ratio was kept at 9.5:1 and the fueling was entrusted to a pair of Dell’Orto PHF 36 carbs, both facing backward and breathing through a real airbox. The Pantah 500 V-twin was very quiet by Ducati standards, and even the beautifully executed Conti mufflers were more civilized than the thundering ones developed for the 750–900 SS V-twin. Quiet, refined, and beautifully smooth, the Pantah 500 V-twin kept the Ducati performance torch bright, generating 49 hp at 9,000 rpm with 31 pound-feet of peak torque at 6,300 rpm. Redline was easily around 10,000 rpm. The whole Pantah 500 SL was lean, featuring a sleek top fairing and weighing 390 pounds, and its speed potential was outstanding, easily exceeding 125 mph, with strong acceleration and midrange response. In terms of top speed it dusted the other hot newcomer of the day, the Kawasaki Z500, by a solid 13 mph.

The Pantah 500 V2 was very elegant from all angles, with forward-facing exhaust manifolds. (Bruno dePrato Collection /)

The Pantah 500 V-twin was Taglioni engineering at its best, but the chassis was standard Ducati, with good structural rigidity, rear-biased weight distribution, and an incredible 30.5-degree rake angle and 125mm trail, to compensate for the inappropriate weight distribution and to grant adequate front end stability at speed. On the road, its handling was acceptable, but when I set up a Ducati Pantah 500 SL versus Kawasaki Z500 comparison test at the Imola track, and pushed the Pantah hard, it proved prone to understeering and the Kawasaki Z500 clocked a better lap time. Still, the V-twin was so incredibly well conceived by Taglioni that it progressively grew in displacement and power, becoming the dominant force in the SBK series in its 1198 Testastretta edition, which featured the Massimo Bordi-designed and developed four-valve desmo heads. But the lower half still featured those angular contact ball bearings and a layout designed by the Old Grand Man. Thank you, Fabio, for the great engineering lesson! 

The evolution to the Pantah 600 SL extracted extra potential from the engine, giving it more torque. (Bruno dePrato Collection/)

And nobody around Borgo Panigale should ever forget that he saved Ducati twice. Once in 1954, when he joined the company and rapidly gave life to the Ducati 100, the first of the celebrated family of SOHC singles that grew to 450cc, and then again in the ’70s, when he designed the formidable Pantah 500 V2, the pillar that sustained the growth of Ducati to its present status. 

Godspeed, Dr. Taglioni.

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