Two Much Trouble: Ducati’s Parallel-Twin Engines

By the mid-1950s, Ducati’s single overhead cam 125cc single-cylinder was the bike to beat in Italy’s hugely popular long-distance road races. An example of its dominance was when factory rider Giuliano Maoggi won the Moto Giro outright in 1956. Over a gruelling 745 miles, he left the entire 175cc class in his wake. But things were different on the world stage, with both the 125cc and 250cc Grand Prix championships reeling from the dominance of NSU’s twin-cylinder racers of 1953-1954.

The NSU twin was destined to have a huge influence on motorcycle racing design, especially for Honda. But unlike Honda, Ducati already had the concept in hand as designer/engineer Fabio Taglioni had first drawn plans for one back in 1950.

The thinking at Ducati in 1955 was if it was going to get serious about world-class racing it needed to look beyond its single-cylinder technology. Its first twin appeared in public at the Milan Show in 1956 and the 175cc racer was entered in the 1957 Moto Giro. Overweight and with a peaky power delivery, it wasn’t competitive and rider Leopoldo Tartarini was probably thankful to be sidelined by electrical issues.

Taglioni used the 175cc as the prototype for a 125cc GP racer and, later, a 250cc version. There is no record of the engine being developed for a road model. Indeed, its complicated design would have made this a risky financial proposition.

The 175 was a distinctive engine and quickly earned the nickname “Il Testone” (Big Head) for its dominant double overhead cam housings. It ran a 180-degree crankshaft, creating a “rocking couple” with much less inherent vibration than a conventional 360-degree throw. Two separate flywheel assemblies were clamped on a central shaft with a spur gear. This activated a series of cogs that eventually drove the camshafts. A jackshaft transmitted drive to the clutch.

It was a complicated assembly that included a serrated-toothed Hirth coupling, a design first used in radial aircraft engines. This system gives a strong connection that is also self-centering, but is very fiddly to assemble. An Achilles’ heel of the design was the large idler gear, which was prone to cracking, leading to top end failures.

An 11:1 compression ratio and peak power produced at 11,000rpm meant things happened pretty quickly inside those cases. It was making 30 percent more power than Ducati’s 175cc single overhead cam single, but it weighed a lot more and had a tiny powerband.

After the abortive Moto Giro, the 175 twin was shelved while Taglioni developed the 125cc GP version, this time using desmodromic valve operation. Ducati’s U.S. importer, Berliner Motor Corporation, took the forgotten valve-spring prototype stateside and raced it in the popular 175cc road racing class. Berliner would go on to play a major role in future Ducati twins.

When the 175cc class died out the little Ducati returned to Italy in the early 1960s, where former factory rider Francesco Villa turned it into a 250. He bored and stroked it from 49mm x 46.6mm to 55.2mm x 52mm and cast new heads and barrels. He also built a new, lightweight frame based on the 125cc GP racer with upgraded forks and brakes. This surviving version is what Phil photographed. Revving now to 12,000rpm and producing 40 percent more power than the 175cc version, it was raced successfully in Italy until Villa moved on to work for Mondial.

The 125GP also stuttered along, with only three built. It was first raced in the 1958 Italian GP at Monza by Francesco Villa. He finished third, amongst four Ducati singles. This wasn’t a good omen and the result wasn’t bettered. In 1959 Luigi Taveri finished in the same position after a year of haphazard development. The twin Phil photographed is the Monza GP bike.

To put this into perspective, Taveri finished fourth in the championship riding both the Ducati twin and an MZ 2-stroke while a young Mike Hailwood finished third on a Ducati’s single, the bike the factory thought had passed its development peak!

The 125 made the same power as the 175 prototype, but at a heady 13,800rpm. This is where the desmo system came into its own, protecting the engine from damage if over-revved, especially on downward gear changes. While it was more powerful than its rivals it was heavier and, again, the powerband was short and hard to hold.

In a rare moment of misjudgment, Stan Hailwood, Mike Hailwood’s father and sponsor, obtained two 125GP twins from Ducati for the 1960 season, but they were a disaster. Meanwhile, Villa’s original 125 was raced and developed in Spain by Ducati partner Mototrans. It received a 15 percent power boost with the rev ceiling increased to 15,000rpm and offering a wider powerband. It was raced well into the 1966 season in both Spanish and Italian national events.

When Stan ordered Mike’s Ducati twins he also commissioned 250cc and 350cc versions. These bigger machines looked similar to the 125, but few parts were interchangeable. Again, they were as powerful as their opposition but heavier and handled so badly that several aftermarket frames were built for them.

The 250 that Phil photographed was sold by Stan Hailwood to John Surtees in 1961. Eventually, Surtees fitted the Ken Sprayson frame and leading-link front forks featured in these photographs.

And so ends the first chapter of Ducati’s dalliance with parallel twins. Ironically, during this period Ducati was carving out a well-earned reputation for tough, competitive, privateer-affordable double overhead cam singles that filled grids around the world.

Paralyzed twin

Strange but true: In 1961, Norton’s designer/engineer Doug Hele repeated Taglioni’s efforts when he produced the 500cc twin-cylinder Domiracer. He saw this as an affordable alternative to the aging Manx single-cylinder racer and with more tuning potential. Despite Norton’s Aussie rider Tom Phillis becoming the first to average 100mph on the TT circuit using a pushrod engine, the project was shelved.

Surely Ducati realized by the 1960s that the twins were a dead end. Well, no. It jumped back into the shark’s pool, this time with its mind on the booming American road market. By 1964 Triumph and BSA twins were roaring out of showrooms across the continent. Oh, to get a slice of this action, thought Ducati management. Its small-capacity, single-cylinder models had carved out an important niche in the world’s biggest motorcycle marketplace. Now it was time to take on the British at their own game.

Urged on by U.S. distributor Berliner and also spurred by news that Benelli and Laverda were developing similar twins, Ducati came up with a 500cc parallel twin, which it displayed as a concept at Daytona in early 1965.

It featured British-like pushrod overhead valve operation and a 360-degree crank, but it had something the Limeys didn’t — an electric starter. Unfortunately, whereas existing British twins were svelte, the Ducati was big, clumsy and sluggish, weighing 418 pounds dry.

Despite a lukewarm response from observers, Berliner, which also distributed Norton and Matchless, thought the design had legs. Remember, these were the pre-Norton Commando days so no obvious all-new British model was on the horizon. The factory persisted and in 1968 it revealed a completely revised version to its American dealers.

This was lighter (392 pounds), more powerful, had a 5-speed gearbox and borrowed a lot of styling from the popular road singles.

Sadly, the time had passed, as Honda’s CB450 twin was already on sale and Norton’s Commando had just hit the market. The U.S. dealers had also heard that Ducati was developing a big V-twin. That made more sense to horsepower-hungry American riders.

The extent of Ducati’s interest with parallel twins between 1964 and 1968 was bordering on obsession. As well as the 500cc, it also experimented with two 700cc concepts, a double overhead cam sports roadster and a pushrod police cruiser.

Ultimately, these ideas came to nothing and sapped the factory’s energy to quickly redesign the 500cc. So the crisply styled and compact 1968 500cc prototype Phil shot in the Bologna factory last year remained just a concept, tucked away and forgotten. It had rarely been seen in public and hadn’t been photographed in detail since 1968.

Another episode had closed in the parallel twin saga that was fast becoming a soap opera.

Twin trouble

Strange but true: How muddled was Ducati management in the mid-Sixties? Fabio Taglioni developed a U.S. police bike that would have become Europe’s most powerful motorcycle. The tire-shredding Apollo V4 ended up as a stillborn prototype — its 100 horsepower engine was simply too powerful for 1964 road tires. A few years later, U.S. police force sales would keep rival Italian factory Moto Guzzi afloat.

So we arrive in the mid-1970s and Ducati, after several changes of management, is cooking up another grand plan. Taglioni’s big V-twins are selling well, but the corporate bigwigs are convinced that the single-cylinder models are nearing the end of the road and the 750cc V-twins are too elitist.

Spurred on by the 1973 oil crisis, a decision is made to develop a whole new range of small, affordable twins. Unfortunately, Taglioni’s suggestion of a V-twin layout is ignored and the parallel-twin plan is reactivated. More years of pain lie ahead.

If Taglioni’s idea had been followed, Ducati’s Pantah would have hit the road five years earlier than it did. The factory had been developing a 500cc V-twin GP racer so all that experience and engineering was waiting to be exploited. But no. It was to be a clean-sheet design, with all the inherent risks involved. Taglioni turned his back on the project and continued developing what would eventually emerge as the 500cc V-twin Pantah.

Following a well-trodden path, other Ducati engineers started with a vibrating 360-degree parallel twin, but soon saw the light and reverted to a 180-degree twin. Their results were revealed at the Milan Show in late 1975. Three models were offered: chain-driven overhead camshaft 350cc and 500cc valve spring versions and a sporting 500cc option with desmodromic valve actuation.

In a classic case of a manufacturer trying to second-guess the market, the least valued option proved to attract the most interest. The Sport Desmo had only been added as a sweetener, but it overwhelmed potential sales of the valve spring GTL models.

Strange but true: Australian importer Frasers commissioned the final run of twins, 67 500cc Sport Desmos produced in 1983. At that time the Pantah was still slowly gathering pace in the showrooms and Aussies liked the Darmah-like styling of the by then obsolete twin. The order of “mini-Darmahs” wasn’t hard to fill as the factory had stacks of unused engines lying around.

In typical Ducati fashion, the Sport Desmo wasn’t available in big numbers until 1977, by which time production had been outsourced to the Italjet factory. Ducati supplied the 350cc and 500cc desmo engines, Leo Tartarini of Italjet the styling and manufacture.

The valve spring GTL models had featured the unloved looks of the 860GT, penned by car designer Giorgetto Giugiaro. Tartarini’s styling was applied to the valve-spring engine and it was relaunched as the GTV in 1977.

While the performance and build quality were underwhelming, the styling helped bring Ducati into a new era of sales and credibility when it was applied to the new V-twin 900 Darmah, also introduced in 1977.

The Sport Desmo models looked fresh and lithe, despite their enormous engine crankcases. Originally designed to contain counter-
balancers for a 360-degree crank, they now incorporated a remote reservoir for the supposedly wet sump engine. This involved complicated internal plumbing, the need for frequent oil changes and keeping a critical eye on fluid levels. This was beyond many owners, with inevitable results.

Although the little twins had rock-steady handling, they were blighted by reliability issues and a short engine life of as little as 12,000 miles.

By the late 1970s, mainstream motorcycling was heading into the big-bore, multi-cylinder Superbike phase led by the Japanese. Even their small-capacity models were now powered by multi-cylinder engines.

When Taglioni’s sports-focused Pantah V-twin arrived, it elbowed the parallel twin out of a very small market niche and the concept was finally put to rest.

Fast-forward a few decades and Ducati finally got the small-capacity twin model right with the Scrambler. Ironically, it’s a leaf out of Taglioni’s original 1970s ideas book: a scaled-down and detuned version of Ducati’s big air-cooled V-twin. MC