The cacophony is difficult to describe, but it sounds something like Maria Callas and Sid Vicious doing a duet, with Yehudi Menuhin on violin and Keith Moon on drums. The discordant racket also tells a story: it is old technology fighting a losing battle with new technology, the Old World retreating before the New World and priceless hand-built exotica buckling under the irresistible force of mass production.

Fifteen-time world champion Giacomo Agostini is stretching the throttle cable of his MV Agusta 500 four as tight as it’ll go, while privateer Stu Avant and his over-the-counter Suzuki RG500 get set to pounce through the Salzburgring’s deadly curves. The Kiwi young gun had paid a mere £10,000 (AU$17,300) for a bike that comfortably beat a machine which was the fastest thing MV’s world-renowned race department had ever built.

No surprise then that this was Ago’s last race as a full-time MV Agusta 500 rider. He had first defected from the aristocratic marque – forged into a legendary racing powerhouse by despotic Count Domenico Agusta – at the end of 1973, when he read the writing on the wall: the four-stroke is doomed. He timed his move to Yamaha with precision, winning the 1974 350 championship on a factory-spec TZ350 twin and the 1975 500 title on the OW26 four, the first premier-class success by a two-stroke.

But despite Yamaha’s historic 1975 victory, the company shut down its factory 500 project for 1976, sending Agostini back into the arms of MV Agusta. Although the two-strokes were clearly faster, Ago still had a close emotional bond with the mechanics and engineers at MV, where he had spent almost two decades as the favourite son of the Agusta motorcycle and helicopter empire. Also, MV and Phil Read had run him close to the 1975 title, so perhaps there was still some life left in the four-stroke.

This was not an MV factory effort, however. Even MV suspected the glory days were over, and was already winding down the race department – the company only agreed to help Ago because he turned up with £250,000 (AU$432,587) of Marlboro cash. The Swiss-based tobacco barons didn’t only choose Ago for his speed, they also wanted him to give them a way into the high-society Monaco party set, where they hoped their cigarettes would be suffused with jet-set glamour.

“I wanted to try again with MV,” says Ago. “But I understood that the two-strokes were getting stronger every year, while all the mechanics in the Cascina Costa workshops couldn’t find any more horsepower. So we all knew it would be a little difficult.”

Indeed. Ago finished fifth in the season-opening French GP, almost a minute behind winner Barry Sheene, riding a factory RG500. The following weekend at the Salzburgring he was sixth, more than a minute behind Sheene and, more to the point, behind four production RGs. That made up his mind – Ago went home and blagged a square-four two-stroke from Suzuki Italia.

For the remainder of the season, Ago’s team crisscrossed Europe in two trucks containing a cornucopia of Grand Prix machinery: an MV 500 and 350, looked after by Arturo Magni and his crew, the RG500 and a factory Yamaha OW31 (for F750 events), fettled by Mac Mackay and Nobby Clarke.

“We took the Suzuki 500 and the MV Agusta 500 to every race,” recalls Ago. “The Suzuki was faster, but I thought that maybe the MV would be better at some circuits, and for sure if it rained I would use the MV, because the power was so much smoother.”

The MV had hardly changed since Read had chased Ago home the previous year. The 56 x 48mm engine made 77kW (103hp) at 14,300rpm and bike the weighed 155kg, with a new duplex cradle frame and upswept megaphones. The production RG made around 10 more horsepower and weighed 15kg less, but it was also incredibly fragile in Ago’s hands: he failed to finish a single GP on the bike. “The Suzuki engine was very easy to break,” he notes.

Agostini had a better, though not much better, time with MV’s 350 four. The smaller engine was a new design with steeply inclined valves and a 16,000rpm red line.

“The MV 350 had a little more power than a TZ350, but the Yamaha was very light and very easy to handle in the corners and on the brakes. I think the MV engine weighed sixty kilos while the TZ’s weighed forty. The first time I rode the MV 350 after I’d raced the TZ in 1974 and 1975, I thought, oh, it’s so slow. My feeling was that it would be impossible to win on this bike, but in fact the lap times were fantastic.”

Unfortunately, the MV 350 was as fragile as the RG500. Ago dropped out of seven of eight 350 GPs with all kinds of gremlins: holed pistons, dropped valves, clutch slip and ignition failure. But he totally dominated at Assen, where he beat Patrick Pons’ TZ by 24 seconds. “Everyone wants to win at Assen and that day the engine was running so good. It was fantastic to win there, with so many spectators and everything.” Historic too, because a four-stroke would never again win a 350 GP.

Two months later the Continental Circus set up camp at the Nurburgring for the season finale. By then Ago was outside the top 10 in both championships, so he had nothing to lose. He rode the Suzuki and the MV during 500 practice. He was faster on the RG around the epic 14-mile ’Ring, but when threatening clouds rolled across the Eifel mountains on race day he chose the four-stroke.

Yet this was not entirely a practical decision. “Okay, for sure the MV would be better in the rain. But also I knew this was almost the end of my career and my last chance to win with an MV Agusta, so it was also an emotional choice.” It was also Ago’s way of thanking Magni and the MV mechanics, who had helped make him the most successful motorcycle racer in history.

RG rider Virginio Ferrari started from pole, but when Ago bumped his four into life he was gone, loudly cheered by the fans, who were getting used to seeing the two-stroke have everything its own way.

“During the race there was only a little rain and that’s always more difficult because you don’t know exactly how fast you need to go,” he recalls.

All Ago did on that day was go faster than everyone else; a lot faster, the MV working much better through the Nurburgring’s damp twists and turns, where its part-throttle performance was still superior to that of the two-strokes. The 1976 season had been hard on Ago. Slow bikes, multiple breakdowns and frequent disappointments had repressed his racing urge, to the extent that he was loudly booed at several races for not trying hard enough. That wasn’t the case at the Nurburgring, where he gave it his all to leave the two-strokes for dead, beating runner-up Marco Lucchinelli’s RG by almost a minute.

“That day I tried very, very hard because I wanted to win the race,” says Ago. “I was so happy because to win again with the MV at the end of my career was very good and very emotional. That day everything was 100 per cent: the engine, the handling, the braking and also the rider, so altogether this is why we had a very good performance.”

Of course, no one then knew that this would be the last 500cc win by a four-stroke. MV’s race department was still ticking over, but without the leadership of Count Domenico – who had died a few years earlier – it was going nowhere fast. Magni, who had run the race shop for 26 years, wanted to design a new in-line four for the 1977 season. Others at MV preferred to press on with the development of a boxer four.

“MV’s years of experience must not be wasted,” wrote journalist John Brown in the 1976 edition of the Motocourse Grand Prix annual. “If everyone gets together, the factory that has recorded a staggering 75 rider and manufacturer world championships will once again reign supreme.”

Not only did MV never reign supreme again, the marque that had won 275 Grand Prix victories over a quarter of a century never even entered another GP. Domenico’s brother Corrado wouldn’t spend the money, perhaps wisely, because the two-strokes were getting faster and easier to ride with every race. The four-stroke era was over, at least it was until MotoGP rights-holders Dorna, the manufacturers’ association and the FIM gave them a 98 per cent capacity advantage over the two-strokes from the start of the 2002 season.

STORY MAT OXLEY PHOTOGRAPHY FRANCOIS BEAU