Du­cati GT750

Bologna beauty

Old Bike Australasia - - CONTENTS - Story and pho­tos Jim Scays­brook Orig­i­nal pho­tos Michael An­drews and Jeff Nield

It seems ev­ery­one was build­ing 750s in the early ‘seven­ties, but few were as pretty as this one.

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 lay­down 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 unI­tal­ian; 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 mo­tocrosssty­le ‘for­ward axle’ mount­ing, com­bined with a 19inch 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.

Smart work

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 four­cylin­der 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 Kenny 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 kick­starter 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

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.

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

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.

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 Bri­tish­sourced 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. Its next out­ing will be the an­nual Du­cati Con­cours Day at the for­mer Hospi­tal at Gladesvill­e on Septem­ber 21 – a day that has ben­e­fited the Hospi­tal’s cof­fers for many years and is ea­gerly an­tic­i­pated by the Du­cati brethren.

ABOVE Dis­tinc­tive tri­an­gu­lar flash on the side cov­ers was for this model only.

Cas­trol Six Hour Race 1972: Kenny Blake (8) on the Ron An­gel-en­tered GT750 leads the sub­se­quently disqual­i­fied Frasers en­try rid­den by Gra­ham Gates, with Brian Clark­son’sMV Agusta (22) on the out­side.

ABOVE Gra­ham Gates on the Frasers GT750 looms up be­hind Owen El­lis’ H2 Kawasaki. RIGHT Kenny Blake’s GT750 leads Greg McDon­ald’s Kawasaki H1 through Dun­lop Loop.

RIGHT The trou­ble­some kick starter, which had a habit of lunch­ing the bear­ing in the crank­case. Later mod­els were beefed up. BE­LOW RIGHT 200mm rear drum brake is cer­tainly up to the job. BE­LOW CEN­TRE RIGHT Gary has man­aged to source orig­i­nal style wo­ven spark plug leads. Aus­tralian-made Lynx air fil­ters were fit­ted to Du­catis of the day. Green plas­tic hose was the stan­dard fit­ment. BOT­TOM RIGHT Leading axle Marzocchi forks were a trade­mark of the GT model. LEFT Orig­i­nal Marzocchi rear shocks are ex­tremely rare.

LEFT Ear­lier mod­els took the drive for the me­chan­i­cal tacho from the front bevel drive cover. ABOVE Veglia in­stru­ments re­placed the ear­lier Smiths. Mileage is gen­uine – not had for 42 years. BE­LOW LEFT No in­dic­ta­tors, but re­flec­tors are iden­ti­cal to those on Nor­ton Com­man­dos.

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