Cycle News - Archive Issues - 2000's

provided in them was not used), while the rear suspension employed a second-generation version of the UniTrak rocker-arm system seen on the KR250/350 tandem twins. The Kayaba monoshock was operated via a rocker actuated by a short, articulated link running from the apex of the triangulated aluminum box-section swingarm. This was aimed at achieving a progressive rising rate to the suspension response, but with a constant rate spring - thus combining sensitiVity to minor bumps with increasing compliance over larger ones, to prevent bottoming out though overheating of the rear shock was an ongoing problem. which meant that Ballington often suffered handling problems as the race wore on. Moreover, in addition to being overweight, with a 1470mm wheelbase, the KR500 was also extremely long, even by the standards of the day - around 4 inches rangier than its competitors - and while this meant it held a line well and was very stable under braking, thanks to reduced weight transfer, it was also quite slow steering on tighter turns. This meant Ballington was forced to run higher corner speeds than his rivals, and losing the front wheel was a constant fear - one reason he was one of the first to experiment with Dunlop's 16inch front tire on a wider 3-inch Dymag magalloy wheel, for a bigger contact patch and better grip than was available from the 18-inch rubber then commonplace, on a narrower 2.5-inch rim. Brakes were Kawasaki's own, with a pair of 290mm steel discs gripped by the company's own twopiston magnesium calipers employing self-made pads, with a single 230mm rear. Like the Suzuki Gamma motor of similar architecture, the Kawasaki's rotary-valve engine measured 54 x 54mm for a capacity of 494.6cc, and like the original RG500 was a true square-four design with the cylinder tilted forward in a single plane on the crankcases, not stepped as on the later Suzukis. All four cylinders were separate, with three-transfer/singleexhaust porting used at first in 1980, switching to a revised five-transfer. layout in 1981, and the fiberglass disc valves fed by side-mounted 34mm Mikuni carbs, just as on the KR250/350, which undoubtedly acted as ongoing testbeds for the KR500 project. Perhaps because of this, there were four separate crankshafts geared together in pairs, with an underslung idler gear driving the dry clutch and water impeller on the right, and the ignition rotor on the left. Kawasaki's own transistorized CDI fired diagonally opposing cylinders in pairs at 180-degree intervals, via double-ended coils located under the large, flat radiator. The six-speed gearbox had no external access, so in order to change internal ratios, the engine had to be dropped out of the frame and split open - still, at 90 minutes, this was not an overly timeconsuming job, and with a choice by (Left) The rotary-valve, square-four design measures 54 x 54mm for a total capacity of 494.8cc, and features four separate crankshafts that are geared together in pairs, with an idler gear driving the clutch and water pump. SIde-mounted 34mm Mikunl carf)s feed the square four's air/fuel appetite. (Above) The hand-welded triple clamps are machined out of alrcraft-grade aluminum alloy. more potent water-cooled piston-port 500cc works triple that saw little action outside of Japan, and whose principal race success remains Mick Grant's 1975 Senior TT victory, in the penultimate Isle of Man TT to count as a points-scoring Grand Prix round, Kawasaki took a breather from the biggest GP category, in favor of focusing on their innovative new design of 250cc and 350cc rotaryvalve tandem-twins. By 1977, these had been honed into GP winners, with Grant winning the first of 73 Grand Prix victories for the Kawasaki twins at Assen that year before handing his seat over to bespectacled South African Kork Ballington for the following season. Together, Ballington and his Aussie teammate Greg Hansford blitzed the two GP classes in '78 and '79, with the South African winning both 250cc and 350cc riders' titles each year, and Greg finishing runner-up in the 250cc class and third in the 350cc both times. Few motorcycles have so totally dominated their chosen GP category as the Lean Greenie tandem-twins did during these two seasons. It was practically inevitable that Kawasaki engineers would hit on the idea of doubling-up their 250cc tandem-twin World Champion to make a 500cc square-four contender, and that's what they did in 1979, testing the prototype rotary-valve KR500 in Japan before moving Ballington and Hansford up to ride the monocoqueframed bike in the 500cc GP class the following season. However, the Aussie's 500cc debut took time to come about, thanks to ongOing problems in the wake of his support for the abortive breakaway World Series, so for the best part of its initial season, development of the KR500 was left entirely in Ballington's hands though he continued to ride in the 250cc class as well, winning five races en route to second place in the final points table behind new team- mate Toni Mang, who actually won one race fewer but scored more points thanks to Ballington's threerace midseason absence due to an intestinal illness that required a stomach operation. In any case, Ballington's main 1980 focus was on developing the new KR500, which suffered from the usual teething troubles of a new design, retiring from its first GP at Misano with a misfiring ignition, then trailing home out of the points (as then was the case) in 13th place in the next race, at Jarama. But by the third GP of the season, the hardworking team of mechanics, including Stuart Shenton (today a race engineer with the World title-winning works Suzuki squad, after more than a decade on the factory Honda NSR500 team), Stewart Baldwin and Ballington's brother Deryck (a.k.a. "Dozy") Ballington had started to extract improved reliability as well as performance from the new bike, which led to its first points-scoring finish at Paul Ricard in Ballington's hands, finishing eighth. Already the brand-new Kawasaki 500 was proving more successful than Honda's infinitely more costly and much louder-trumpeted - concurrent NR500 oval-piston four-stroke project, which also used a monocoque chassis design, but to lesspositive effect. However, Ballington's abdominal operation then sidelined him for the next two 500cc races but fifth place on his comeback in Finland was just the fillip the team needed, followed by seventh in the British GP at Silverstone. The KR500's short debut season ended on a down note, though, with both Ballington and Hansford retiring probably thankfully - from a damp race at the old 14-mile-long Nurburgring circuit, with handling problems occasioned by broken steering dampers. Ballington survived the ensuing tankslapper only narrowly, breaking the screen with his forearm as he wrestled the bike back under control, to wind up in one piece and 12th in the final 500cc World Championship table. Though innovative in design and increasingly powerful, the 1980 Kawasaki suffered from a lack of acceleration out of slow corners, most likely due to its relatively porky 303-pound dry weight: "Initially, at the start of the season we had a deficiency in high-speed acceleration, too, as well as top speed," said Ballington at the time, "but we made a lot of leeway up after the French GP early on, and there was only a few mph in it by the end of the season. But coming out of slow corners was still a problem, and the heavy weight which contributed to that meant you also needed a good deal of physical effort to throw it around tricky circuits. At the Nurburgring, I must have lost a couple of pounds a lap through perspiration - I reckon the monocoque frame is strong enough for a two-liter engine!" Designer Kinuo "Cowboy" Hiramatsu's beautifully arc-welded light-alloy monocoque chassis followed the Ossa 250 design route in incorporating an eight-gallon fuel tank mounted in the conventional position, rather than the Formula One car-type construction of the John Player Norton chassis of just six years earlier. Nevertheless, the Kawasaki's fabricated chassis delivered tremendous torsional and lateral stiffness - much more so than the tubular-steel frames then commonplace on rival machinery - with two outer side plates bolted to the rear flanks of the tank to support the footrests as well as the rear swingarm pivot, and cross-braced to an inner pair of plates attached to the back of the fuel reservoir. The 35mm Kayaba forks mounted in Kawasaki's own fabricated triple-clamps were held in a pivot mount welded to the front of the chassis (though the air damping a u a I e n e _ S • NOVEMBER 6, 2002 21

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