It seems everyone was building 750s in the early ‘seventies, but few were as pretty as this one.
Story and photos: Jim Scaysbrook • Original photos: Michael Andrews and Jeff Nield.
By the time Fabio Taglioni’s new V-twin engine began testing in July 1970, Ducati was in deep financial trouble. This gamble had to work. Government owned since 1969, Ducati, like all the European, British and American manufacturers, was fighting a pitched battle against the Japanese. This had been tough enough when the battle had been confined to the smaller capacity classes, but since the arrival of the CB750 Honda it was a whole new ball game. Ducati knew they needed a big bike, but they also knew that Taglioni’s 1,260cc V-4 Apollo wasn’t it. In the mid-1960s the company experimented with the idea of a parallel twin, and went as far as displaying a mock-up of one at the 1965 Daytona Motorcycle Show. Nothing further was heard of the twin until a re-vamped 700cc version was briefly kite-flown a couple of years later before being quietly forgotten.
It was a case of swim or sink, but Ducati, or more specifically Taglioni, knew it needed something special to stand out in what was becoming a stampede of new models. The Kawasaki Z1 was about to hit the market, so out-doing that with a transverse four was out of the question, Triumph and BSA had their triples, Norton its ageing twin. What Taglioni came up with was essentially a pair of 350cc single-cylinder engines mounted on a common crankcase and it proved damn-near perfect straight away. The standard 350 bore and stroke of 76mm x 75mm was slightly altered to 80 x 74.4, but the heads followed the factory’s time-honoured tradition with single overhead camshafts driven by helical-cut bevel gears driven by shafts. The camshafts were suspended on ball bearings, with replaceable shims on top of each valve stem, as on the 250cc Mach 3 model. Unlike the singles which used hairpin valve springs, the 750 used coil springs. Taglioni favoured this layout since it produced only minimal vibration through a near-perfect primary balance, and the lay-down front cylinder provided a steady flow of cooling air to the almost upright rear cylinder – always a bugbear with conventional v-twins. The layout became referred to as an L-twin, and still is.
Downstairs in the vertically-split crankcases, the front, almost horizontal cylinder was offset to the left from the rear cylinder, with a pressed-up crank assembly with the one-piece conrods on caged roller big ends. The crank assembly sat on hefty ball bearings, with a helically-cut primary gear on the left side transmitting power to a wet clutch and the five-speed transmission. On the right side, sits the 150-watt generator and a vane-type oil pump – the pump driven by an idler gear which meshes with a spur gear on the right side of the crankshaft. The wet sump contained 4.5 litres of oil and meant there were no outside hoses or oil tank, and theoretically at least, no oil leaks.
Initial testing went without a hitch and by September a complete motorcycle existed. In November it was unveiled to a slathering press at the Milan Show. That motorcycle, dubbed the 750GT, had clip-on handlebars and a Fontana double-sided front brake, but by the time production began in mid-1971, a single cast iron disc gripped by a Lockheed caliper was up front, and the clip-ons had given way to a conventional flat tubular steel handlebar. Early production versions used Spanish-made Amal 930 30mm carburettors although fuel injection was briefly tested in early 1972, before switching to Dell’Orto’s new version of a concentric-style carburettor.
One aspect of the new design was decidedly un-Italian; the frame. In February 1971, a frame built by Colin Seeley in England was sent to Ducati and built up around their 500cc Grand Prix v-twin engine, to be ridden by Bruno Spaggiari and later in the season by Phil Read, who looked set to score a surprising second place (after Agostini’s MV had dropped out) at the Italian Grand Prix at Monza until he ran low on fuel. The same company supplied the frame for the prototype 750GT and for the company’s entry into the booming Formula 750 racing class. The production chassis was made from seamless, chrome molybdenum steel tubing, with the rear members providing the mounting bosses for the swinging arm rear suspension. To increase rigidity in the swinging arm, the rear chain adjusters ran inside the tube itself, which was the usual Seeley practice.
A fundamental issue with the so-called L-twin design was an inherently long wheelbase, due partially to the need for clearance between the front cylinder head and the front wheel. To minimise this, Taglioni mounted the gearbox mainshaft and layshafts on top of each other, with a set of helical gears coupling the mainshaft to the crank. The bespoke 38mm Marzocchi forks featured motocross-style ‘forward axle’ mounting, combined with a 19-inch front wheel, which gave the GT a raked-out, rangy look. The resulting 1562mm wheelbase was still on the long side, but the best that could be achieved under the circumstances.
Final specification for the bodywork varied market to market. Styling was entrusted to Leopoldo Tartarini’s Italjet concern, and quite radical changes were made to the style that had been shown in Milan and on the various test mules. UK laws required a steel fuel tank, whereas a fibreglass tank was used elsewhere, including Australia. Ducati at the time had a fixation with fairly garish metalflake colour schemes, as had been seen on the singles, and the gold décor was carried over to the GT in most export markets, while the standard European/UK finish was red. An American market version was offered with higher handlebars, and police versions with a high windshield, single seat, panniers and equipment racks also took up duty with law-enforcement agencies in Europe.
Sunday 23rd April, 1972 was a red-letter day in Ducati’s history, and a marketer’s dream for the new 750. The Moto Club Santerno had jumped in at the deep end to promote Europe’s version of the Daytona 200, for 500-750cc machines at the vineyard-lined Imola circuit, just 35km from the Ducati factory. A world-record $50,000 prize money fund lured a packed field of 42 competitors. Although most pundits dismissed the Ducati effort against the likes of factory teams from Kawasaki, Triumph, Moto Guzzi, Laverda and Norton (plus a special 750cc four-cylinder MV Agusta for Agostini), Ducati were out to impress, turning up to the circuit for Friday’s practice with a glass-sided mobile showroom containing no fewer than seven sparkling 750 racers. At the last minute, the US Kawasaki team opted-out of the race, leaving contracted rider Paul Smart on the sidelines, and Ducati pounced immediately, signing the British star alongside Spaggiari. Smart repaid the favour by qualifying second to his new team mate, with Agostini third on the grid. Within one lap Smart had blasted past Agostini for the lead, followed soon after by Spaggiari, and that’s the way it stayed, with the Englishman taking the flag 4 seconds ahead after averaging 97.71 mph for the race and pocketing almost $10,000 for his trouble. To say Ducati were over the moon at the result is a massive understatement – Smart was presented with his winning machine as a sign of their appreciation! Spaggiari’s sister machine was sold to Australian importer Ron Angel, who put Ken Blake on the famous bike for races in Australia.
The fairy tale result was just what the doctor ordered, and orders cascaded in for the new 750GT. The lack of an electric start was seen as a slight drawback (the new Guzzi V7 had push-button starting), but fortunately the GT was an easy kick-starter once the technique had been perfected. As journalists clocked up the kilometres, reports swimming in superlatives flowed around the world. Everyone seemed to love the engine characteristics, and especially the unique throaty bark emitted by the Conti mufflers. Ground clearance did not seem to be a major issue, and despite the long wheelbase and the fact that around 15kg had been added to the weight of the prototype, the GT handed like a dream and stopped well. Drawbacks? Well, the electrics were a bit…Italian…and despite the almost universal changeover to left-foot gearchange, the GT stuck with a right side shift.
Hardly surprisingly for a design this good straight out of the box, Ducati quickly went to work on variations of the theme. The 750 Sport – a luscious looking machine that appears just as glamorous and svelte today as it did more than 40 years ago – appeared in late 1972, still as a valve spring motor and using the same cycle parts as the GT but with clip-on handlebars, single seat and rear set footrests. The Sport had a tweaked engine with 9.0:1 compression, 32mm Dell’Orto accelerator-pump carburettors and a higher top speed. The Sport soon evolved into the desmo 750 Super Sport (SS) in 1973, and thence into the fabled 900 SS, all of which closely adhered to Taglioni’s landmark design.
By the time the final versions of the 750GT left the factory in 1974, an electric starter was standard fitment, as it was on the model’s replacement, the chunky looking and fair less dainty 860GT.
Good and bad at Amaroo
After the triumphant display at Imola, there were high hopes for a good showing for the GT750 in true production form at the third running of the Castrol Six Hour Race at Amaroo Park on October 15, 1972. Stocks of the new model were still in short supply, but two made it to the track. Victorian importer Ron Angel entered one for Kenny Blake, with Jeff Curley listed as the second rider (although Blake did all the riding in the race), and Sydney dealers Frasers had Graham Gates and Gordon Lawrence on another.
The GT750 actually made its local debut in June 1972 at The Advertiser Three Hour Production Race at Adelaide International Raceway in the hands of Blake and veteran Eric Hinton. After running strongly in the first hour, the Ducati gradually slipped down the list and was eventually dropped by Blake on the notorious off-camber left hander entering the ‘Speed Bowl’.
In the race, the hard-riding Gates kept the Frasers machine in the top group, and held fourth place by half distance, with Blake in sixth. But although both bikes finished in fourth and sixth place respectively, officials pounced after the chequered flag and impounded the two Italian machines. Blake’s was found to be standard, and he moved up to fifth outright after Joe Eastmure’s Suzuki T350 was disqualified, but when the Frasers entry was measured, it was found the be considerably oversize – by around 100cc! It was subsequently proven that Ducati 450 pistons had been substituted, which went some way to explain the bike’s amazing turn of acceleration up Amaroo’s hill, and the bike was disqualified (moving Blake up one further place, to fourth) with the riders and entrant all losing their competition licences. By this time of course, all the spectators had gone home, chattering excitedly about the incredible speed and reliability of the new Ducatis!
Aussie delivered, Euro aimed.
Gary Peters’ GT750 is somewhat of a rarity in these parts. A 1972 model, it was delivered new from Frasers, Sydney in early 1973 to Steve Gobert, father of Anthony, Alex and Aaron – all successful international racers in various forms of the sport. “Rumour has it that the bike almost cost him a divorce,” says Gary, “Because the deposit for the house went on the purchase. When Steve passed away some time back, Dave Ward from Moto Italia bought three Ducatis from the Gobert family, including this one and Anthony’s gifted 916 for winning in the AMA series in USA. Dave rode the GT regularly and I bought it from him three years ago. It needed a cosmetic restoration but was pretty much OK. These Euro-spec 1972 models were available in red or black, with what the Americans called the ‘Lazy S’ – the black zig zag on the tank, and the triangular flash on the sidecovers. After that they went to the yellow colour for the Australian delivered models, and the tank was a different shape – the later ones were metal, not fibreglass. One thing that is distinctive on this model is the kick starter which is a strange angle and used to fail regularly, along with the kick starter bearing on the crankcase itself which was later modified. The petrol tank on the earlier models (as used in the 1972 Castrol Six Hour) were taller at the back and the knee indents were a slightly different shape”.
Gary’s GT750 is fitted with the later Dell’Orto pumper carbs (32mm instead of the original 30mm), but would have originally had the unloved Spanish Amals – a knackered set is in Gary’s workshop. He laments chucking away the original air filters fitted to the Amals, which are today unobtainable. “The Dell’Ortos work much better, but I will refurbish the old Amals and fit them for concours events only. The filters fitted to the Dell’Ortos were actually made in the period by Lynx Engineering. This model came out without indicators, but used Lucas reflectors – the same as fitted to the Norton Commando. I bought a new GT750 in 1973 and it had indicators fitted, so this model is the last to come out without them.”
Original Marzocchi rear shocks are fitted, and these are also rare today, as they had a propensity to blow seals and were generally replaced with Konis or Girlings. The deep red paint was applied by Crowe’s Custom Paint in Sydney’s Beverley Hills, and the original, rather intricate orange-edged black stickers were made by Dan Murdoch. An electronic Veglia tacho is fitted, although earlier models used a Smiths mechanical tacho (and matching speedo) with the drive from the front cam box cover. Another British-sourced feature is the Lockheed front disc brake and master cylinder, which soon gave way to a Scarab unit and eventually to Brembo. “The Scarabs were the worst of the lot,” explains Gary. “They used to get corrosion inside and lock up without warning – there were lots of accidents. Today you can restore the Scarabs with modern materials for the pistons and modern seals. These models also had a fragile gearbox. I remember Gordon Lawrence used to race one in the Chesterfield Superbike Series at Amaroo Park, and every lap when he would accelerate out of the dead-stop corner it would jump out of gear. When my bike was rebuilt in the early ‘nineties by Gowlanloch’s they put a new first gear in it, even though it hadn’t done very many miles. I think Steve Gobert had fallen off it once or twice, because the tank had been repaired, but he was a spray painter so he did his own repairs. The original transfers were just water-based so they washed off the first time they came in contact with petrol, but these are absolutely correct computer generated replicas – Dan Murdoch got all the correct numbers from America.”
Gary reckons there wouldn’t have been more than a dozen or so of this particular model brought to Australia. “The very first Ducati I ever rode – one of this model – when I was 16 I went down to the dealer and although they wouldn’t let me ride it they gave me a pillion on it and I was absolutely in love with it – the next year I just had to have one. I had a Kawasaki H1 at the time, one of the orange ones, and amazingly I survived, so I traded that on a new GT750.”
That 40-year-old love affair shows no signs of waning, and Gary’s superb GT750 draws crowds whenever it appears.
Ducati 750GT – Specifications
Engine: 748cc, 90º v-twin. Single overhead camshaft, bevel driven.
Bore x stroke: 80mm x 74.4mm
Compression ratio: 8.5:1
Power: 65 bhp at 7,500 rpm.
Transmission: Gear drive to wet multi-plate clutch. 5-speed close ratio gearbox, chain final drive.
Frame: Double cradle tubular steel with engine unit as stressed member.
Suspension: Marzocchi front forks with two-way damping.
Rear: Marzocchi units with 3-position spring preload.
Brakes Front: Single 280mm disc with two-piston caliper.
Brakes Rear: 200mm single leading shoe drum.
Tank capacity: 20 litres
Max speed: 123 mph
Price new in Australia (1972): $1599.00
Years produced: 1971-1974
Total production: 4,093