YZR500 ine 0familyl THEOW6
Yamaha’s RD56 factory racer which took Phil Read to the 1964 250cc World title really did use a discvalve motor which profited from MZ technology - purloined by Suzuki from the DDR’S MZ, by enabling its rider-engineer colleague Ernst Degner to defect to the West in 1961 – that tech was widely shared and with Suzuki and Yamaha both based in Hamamatsu, Japan it’s not hard to imagine how that came about… But when Yamaha finally entered the 500cc category in 1973, the OW19 in-line four which Jarno Saarinen took to victory in its very first race in the French GP at Paul Ricard, was a piston-port design. In 1975 Giacomo Agostini gained GP racing’s ultimate prize for Yamaha, which with the piston-port OW26, became the first Japanese company to win the 500cc World title. And while its Suzuki neighbours then gained the upper hand courtesy of Barry Sheene who won the championship in 1976/77 with the rotaryvalve square-four RG500, Yamaha struck back in 1978, when Kenny Roberts won the first of his three World Championships with piston-port Yamahas. By then, Yamaha had already ceded dominance of the 250cc and 350cc classes to the rotary-valve Kawasakis, and Roberts’ 1980 500cc World title on the OW48R had been a close run thing, with the increased performance of the disc-valve Suzukis providing a lesson that Yamaha decided they needed to learn for Roberts to keep winning. The rotary-valve format provides greater potential for outright power via assymetrical inlet timing, so Yamaha adopted this to redress the performance gap that had opened up between their piston-port OW48R, and the Suzukis. So for 1981 they effectively produced a copy of the rotary-valve RG500, the square-four OW54 - leaving the uprated OW53 version of the piston-port OW48R inline four to provide support for Roberts from Marc Fontan and Barry Sheene in defending his title. After a disastrous debut in Austria, Roberts won the next two races in a row in Hockenheim and Monza with the square-four, after his engineer Kel Carruthers had radically altered the cylinder porting.
It was ahead of its time. In many respects, it still is.
Although KR still didn’t care for the more sudden power delivery compared to what he was used to – this was the first time he’d ever raced a disc-valve machine, of any capacity – it was evident that Yamaha’s bet had paid off. But a series of handling problems mainly due to the Goodyear tyres Kenny alone used, he finished third in the points table behind new champion Marco Lucchinelli, and Randy Mamola, both on Suzukis. Barry Sheene did win the final race of the season in Sweden on a rotary-valve OW54, though. For 1982 Yamaha recruited Graeme Crosby from Suzuki, and produced a heavily updated version of the rotary-valve square-four, termed the OW60. This featured an improved version of the OW54 motor in a new square-section tubular aluminium frame fitted with progressive-rate rear suspension via a bell-crank operating the fully-adjustable Kayaba rear shock, as Yamaha’s response to Suzuki’s effective Full Floater rising-rate rear end.
A total of eight bikes were built; two each for Roberts, Sheene, Crosby and Sonauto Yamaha’s Marc Fontan, who was to win the French 500cc title on the bike but could only finish tenth in the World series. Roberts won his first-ever GP race in Argentina on Dunlop tyres aboard the OW60, with Sheene second on a similar bike that KR declared was significantly better than the OW54, and now handled properly thanks to the new suspension layout. That being so, it seems strange this was the last time he ever rode the 500 squarefour, instead choosing to grapple for the rest of the season at his own insistence with the new OW61 which Yamaha had developed. This was still a disc-valver, but with a V4 engine format aimed at lowering the centreof-gravity with more compact architecture. The carbs were relocated within the vee rather than hung off either side, making a wider, less aerodynamic bike. Though KR won the Spanish GP at Jarama on the new bike, it was only thanks to an immense physical and personal effort that he now looks back on as one of his greatest results, aside from that the rest of the season was a write-off for him: “The OW61 was the worst racing motorcycle Yamaha ever made,” stated no less an authority than Kel Carruthers: “The OW60 was a good machine, much lighter than the over-engineered OW54, and it had a decent chassis, too. Kenny would have been World champion in 1982 if he’d ridden that bike all year.” While Suzuki’s Franco Uncini was the ultimate beneficiary of that in winning the
1982 500cc World Championship, Yamaha’s Graeme Crosby clinched second in the points table without actually winning a race, though he did double up on his Daytona 200 victory by taking victory in the Imola 200 on his OW60. Sheene and Roberts tied for fourth place in the table.
In creating the OW60, Yamaha may have set out to faithfully copy a Suzuki RG500, but – having ridden both bikes I believe that they actually did the better job out of the two – even if the results sheet of the 1982 World Championship says otherwise. But the Yamaha is the best of both worlds. With a short, low-set engine which compacts the mechanical mass of the bike to best advantage for optimum handling, especially in changing direction from side to side. It also has extreme forward weight distribution for maxing out turn speed, without affecting stability or drive - but thanks to the YPVS powervalve system, which Suzuki took another three years to emulate - it has a torquey pickup from down low. Combine that with a smooth transition into the powerband, combined with the top end power of a rotary-valve motor and it’s a potent and accomplished powerplant. This is a very clever bike which deserved to be more than a one-year wonder. It could have – should have? - been a champion…