DUCATI 500 BICILINDRICA
Fifty years ago, Ducati’s first-ever V-twin racer, the 500 Bicilindrica, gave the world a glimpse of the marque’s future rise – and an entire new range of 750 and 900cc machines based around the same engine configuration
The V-twin racer that shaped the future of the Italian marque
With its first public appearance in 1971, Ducati’s 500GP Bicilindrica racer was on a mission – to familiarise the public with a novel engine layout for a sporting street bike. In the five decades that followed, the Bologna company would become synonymous in the common consciousness with the 90° V-twin powerplant – both in production-based racing and road machinery – but this was where it all started.
The stakes were high – Ducati was fighting for survival as a fully State-owned company with declining production figures. But new company President/ceo Arnaldo Milvio and General Manager/coo Fredmano Spairani were both road racing fans, and in October 1970 had secured agreement from Rome for Ducati’s official return to Grand Prix racing – a mere five months prior to the 500 Bicilindrica’s race debut at Modena on March 14 of the following year.
Ducati’s legendary engineer Fabio Taglioni already had a design roughed out – and after much hard work by the small Ducati Reparto Sperimentale, it was translated into metal, tested and readied in time for that Modena Italian championship round. He had adopted the 90° V-twin format to achieve a reduction in vibration due to the cancelling out of primary inertia forces and superior cooling of the rear cylinder. The Bicilindrica’s 499cc V-twin was also no wider than one of Ducati’s existing 250 singles (with which it shared the same 74 x 58mm cylinder dimensions), so the bike’s reduced frontal area also gave lower fuel consumption and increased performance due to more efficient air penetration.
On the new bike, factory stalwart Bruno Spaggiari found himself embroiled in a battle for third with Roberto Gallina’s speedy parallel-twin Paton behind the MV Agusta triples of Giacomo Agostini and Angelo Bergamonti. Things looked very encouraging, although gearbox problems slowed Spaggiari to sixth while team-mate Ermanno Giuliano retired.
Five 500 Bicilindricas were built during the three years the bikes raced, predominantly using valve-spring rather than desmodromic engines. They also varied between singleoverhead-cam two-valve and four-valve versions, each sharing the time-honoured Ducati cylinder head design, with a vertical shaft and bevel drive up the right side of each cylinder.
Both shared the same bottom end – a scaled-down version of what became Ducati’s traditional wet-sump V-twin design format, with a roller-bearing big-end and both conrods sharing a common crankpin, albeit positioned side-by-side
on it rather than ‘knife and fork’ as on a Harley. The 90° V-twin’s trademark differential cylinder finning was employed for cooling purposes – though as power rose, overheating of the rear cylinder with the full fairing fitted must have occurred, because later bikes had two slots in the leading edge of the fairing which forced air via flexible tubing to the rear cylinder. This was in addition to the ‘letterbox’ slot under the front numberplate leading to the nose-mounted oil cooler.
The 500 V-twin’s narrower crankcase than the 750’s wasn’t just as a result of the smaller capacity, but also because, with no alternator to be driven, a shorter crankshaft could be used. A gear-driven oil pump lay on the right of the engine, just below a short bevel shaft which drove the twin contact breakers for the coil ignition eventually employed, after problems with the transistorised electronic ignition sourced from the company’s sister firm, Ducati Elettronica. Apart from providing a fatter spark, Taglioni experimented with this to save weight, since with total-loss coil ignition the use of twin-plug heads (with a second small 10mm plug nestling beside the vertical camshaft drive) dictated fitting four threevolt coils and two six-volt batteries, one each side of the engine. Thus equipped, the 500 Bicilindrica initially weighed 138kg dry, with 18in Borrani alloy-rimmed wheels fitted from the start, a single cast-iron 280mm (11in) Lockheed front disc brake, and a 230mm Fontana cast aluminium twin-leading-shoe rear drum.
The included valve angle on both sohc versions of the 500 Bicilindrica was a wide 80°, rather than the 60° of the racing 750/900cc V-twins and later Pantah road models, with paired valves and an old-style pent-roof combustion chamber on the four-valve motor. This featured a domed piston design with deep valve inserts, while on the two-valve version a flat-top slipper piston was used, with less pronounced valve cutaways. Squish bands were featured on both the combustion chamber and the pistons of each type of engine. A dry clutch was adopted from the start, with a six-speed gearbox with gear primary drive, but a detachable, separate gear selector box with a magnesium outer casing (like the clutch housing), while the rest of the engine castings were in aluminium.
Twin 40mm Dell’orto carburettors were fitted, originally each with a separate circular float chamber, but these were replaced for 1972 by the new PHM40 Dell’orto concentrics, bolted directly to the cylinder heads. On both versions these carried short, spun aluminium velocity stacks, whose use was good for a couple of extra brake horsepower.
The four-valve engine did not yield the hoped-for superiority in output over the two-valver, though it did rev to 12,500rpm
‘THE MODENA DEBUT AUGURED WELL FOR THE FIRST V-TWIN DUCATI EVER SEEN ON TRACK’
safely (versus an initial 11,500 limit for the two-valver), and started out delivering 65bhp to the rear wheel at 11,500rpm. This compared to 61.2bhp on its Modena debut for the twovalver at 11,000rpm, with a relatively broad powerband from 6000rpm upwards. By the end of 1972 the output was raised to 71bhp at 10,500rpm in its final sohc form, compared to just 69bhp for the less flexible four-valve unit. A desmo version was also produced for 1972, but soon dropped because there was no significant increase in performance.
The Modena debut was the first ever race track appearance of any Ducati V-twin motorcycle, and it augured well for the future. However, while Spaggiari’s Modena bike comprised a two-valve sohc engine in a Verlicchi-built frame of Ducati’s own design, contrary to Taglioni’s wishes Spairani had been convinced by the firm’s British importer Vic Camp that UK frame specialist Colin Seeley was the man to do the job of wrapping it in metal. Thus when Milvio and Spairani attended the Racing and Sporting Motorcycle Show in London in January 1971 (where Vic Camp displayed the 750GT V-twin for the first time in Britain), they visited the Seeley factory, as Colin Seeley recounted, before recently passing away. “Arnaldo Milvio had announced at the Show that Ducati was going to order two prototype frames from Colin Seeley Race Developments for their forthcoming 500cc V-twin race engine,” said Colin. “Obviously, this was a very exciting project for us to be involved with, working directly with one of Italy’s leading manufacturers. Fredmano Spairani came to see us at our little works at Belvedere in Kent, just across the river from Vic Camp in Walthamstow, who’d been kind enough to recommend us.
“Spairani brought a set of outline drawings of the engine, and some bare engine castings, plus a pair of carburettors. It was the first time I’d ever seen such an engine, but I liked the overall layout, which allowed us to produce a pretty slim motorcycle, not really any wider than a Seeley G50. Our designer Bob Cakebread got busy with drawing up the prototype frame unit, and with a bit of overtime our framebuilders Jack Wren and Denny Barnes finished the job five weeks after we received the order, so it was ready for dispatch a week earlier than promised.”
The Seeley frame, in Reynolds 531 manganese-molybdenum steel tubing, was based on his MKIII chassis for the Matchless G50 engine, for which Seeley had acquired the manufacturing
rights when he bought the AMC racing department in 1966.
Seeley’s Ducati frame consisted of twin top tubes extending back at a narrow angle from the cylinder head, with a similar braced pair running down from the steering head to the swingarm pivot, wrapping around the engine’s rear cylinder. A pair of small-diameter tubes originally joined the two runs beneath the seat, passing close by the rear carburettor, but these were later dispensed with. A final pair of tubes ran down from the rear of the steering head to bolt to the front of the protruding finned oil sump, leaving the lower part of the frame open, and thus using the engine as a semi-stressed member. A tubular steel swingarm with pull-type axle adjusters completed this light and very rigid design weighing just 9.5kg. Taglioni immediately adopted the Seeley swingarm design on Ducati’s own frame for the 500GP bike, as well as on the new 750GT street model and the F750 race version!
Spaggiari and Giuliano gradually began to make their mark with the 500 V-twin. Giuliano finished second behind Agostini’s MV in the prestigious Imola Gold Cup on April 12, after Spaggiari had retired when not far behind the MV, with his bike jumping out of gear. The following week at Cesenatico, Giuliano repeated the result after Spaggiari’s engine suffered a spectacular blow-up while he was dicing with Ago for the lead. Phil Read, looking for a 500cc ride, was sufficiently impressed with the Ducati’s performance to ask Spairani for a ride. He agreed Read could have a bike for Silverstone’s John Player International in August.
Not long after, Gilberto Parlotti scored what was to prove the 500 Bicilindrica’s only race victory on May 30 at Skopya Locka in Yugoslavia, using the engine with four-valve heads fitted to the Seeley frame. Spaggiari was third on the Ducatiframed two-valve variant.
Ducati’s unique glass-sided transporter made its way to Britain with seven bikes inside – a mixture of 500GP and prototype 750 V-twins. First stop was Snetterton, a fast, open circuit similar to Silverstone. Vic Camp’s rider Alan Dunscombe tested the Seeley-framed bike there, now with the two-valve motor installed, reporting that the rev limit had been raised to 11,800rpm but the powerband narrowed so that strong, useable power only came in at 9000 revs.
Bruno Spaggiari was also in attendance, riding a variety of bikes, and Colin Seeley himself was allowed a couple of laps aboard his creation. “I found the bike fast, smooth and impressive,” commented Colin afterwards. “Ducati seemed happy enough, and ordered a second frame from me right there and then, so that afternoon it was back to Belvedere,
‘GILBERTO PARLOTTI SCORED WHAT WAS TO PROVE THE 500 BICILINDRICA’S ONLY RACE VICTORY IN MAY 1971 USING THE ENGINE WITH FOUR-VALVE HEADS’
overalls on, welding torch alight, and get cracking!”
The following week, on June 30 at Brands Hatch, Read got his first ride on the Ducati 500, sampling both Seeleyframed and Verlicchi-chassised bikes and expressed a preference for the Seeley-framed version, duly committing to riding it at Silverstone on August 22 – the British mainland’s major short curcuit event at that time.
Read had hurt his shoulder at the Brno GP on his Yamaha, but reported fit to partner Spaggiari in the 500cc race at Silverstone, where they both raced two-valve engines fitted in Seeley frames, although both retired after having each at one time held third place behind Ago and the Suzuki TR500 two-stroke twin of rising star Barry Sheene – Read with big end problems, Spaggiari with electronic ignition failure.
Mike Hailwood, by now racing cars full time with the occasional bike race slotted in, also got to ride both the 500GP V-twin and Ducati’s barely-completed prototype 750 desmo in Thursday practice at Silverstone.
“Spairani asked me at the last moment to build Ducati a third frame, but this time for the first-ever desmo race version of their 750 V-twin, with a six-speed gearbox,” said Colin Seeley. “Vic Camp furnished us with a 750GT engine to build it around, and we worked literally night and day to get it finished on the Monday before the race, August 16, when we delivered it to Vic’s.
“The Ducati mechanics based there descended on it, and had the machine built up in time for Mike to ride it at Silverstone three days later. But even though he recorded the sixth fastest Formula 750 time on a bike which hadn’t existed three days earlier, he decided not to race it as the handling was ‘not to my liking’. But he made a point of coming to find me to tell me that this was no implied criticism of my handiwork. ‘Once sorted, it’ll be a good ’un,’ he said. What foresight!”
The first year of the 500 ended on an encouraging note at San Remo on October 10, when Read, Parlotti and Giuliano finished in line astern behind Ago’s MV triple, and ahead of the increasingly large number of 500-class two-strokes. However, all at Ducati recognized it would never be an Mv-beater, and while yielding valuable information for the production 750cc version, the 500 twin would have to become a four in order to get on terms with Agostini.
Spairani immediately laid plans to go after the all-conquering MVS with a four-cylinder 500 Ducati, and a 350 triple derived from the same platform. After some wrangling, the 500 four was sadly dropped, and the 350cc engine, initially developed by the UK’S Ricardo Engineering, proved disappointing.
The new Formula 750 class created for 1972 had been a category tailor-made to accord with Taglioni’s preferred technique of developing new street models through racing. Moreover, winning the big-money Imola 200 on the company’s home ground on April 23 inevitably became a key target.
Nevertheless, occupied as he was with the F750 bike, Taglioni still found time to produce an updated version