High performance two-strokes have long disappeared on the street but when the RZ500 appeared in 1984 it marked a new era in motorcycling. Soon Suzuki and Honda followed with replicas of their awesomely fast and intimidating Grand Prix racers, but Yamaha was the first, and the RZ500 arguably the best.
During the late 1970s and early 1980s Honda blindly pursued the domination of the four-stroke in Grand Prix motorcycle racing but Yamaha eschewed such unlikely ideals. Yamaha was always the champion of the two-stroke, and they proved devastatingly successful. It was Yamaha that dethroned the dominant MV Agusta in the premier 500cc class in 1975.
They then followed this with Kenny Roberts’ three consecutive 500cc titles from 1978 until 1980. Yamaha’s 500 GP racer evolved into a V four and Kenny Roberts very nearly won the 1983 500cc World Championship. Yamaha then stunned everyone by offering a road going replica of Roberts’ machine. There had been other race replicas, but the RZ500 was the first real Grand Prix replica.
Technologically the RZ500 was in a completely different league from any other production motorcycle in 1984. The specifications were mind-blowing. Just like Roberts’ GP bike the water-cooled two-stroke was a 50-degree V-four with two crankshafts geared together. Equipped with Yamaha’s YPVS exhaust power valves and reed valves, four 26mm Mikuni carburettors were mounted on the side of each cylinder.
It wasn’t quite exactly the same set-up as the factory racer but was enough to produce 90 horsepower at 9,500 rpm. The dual primary drives were geared directly to a huge clutch, while the front crankshaft spun a counter balancer to smooth out unwanted high frequency vibration. A removable cassette-style six-speed gearbox was also just like the GP bike, as was the explosive nature of the power delivery.
Two-strokes were known for their peaky power delivery and the RZ500 was no exception. Despite the power valve there was little power below 6,500 rpm, the engine screaming immediately to the 10,000 rpm redline. The RZ500 was not a relaxing machine to live with, behaving like a missile on a short fuse.
The chassis was also unusual for the early 1980s. One of the first production motorcycles to feature a perimeter-style frame (box-section steel), because there was no room under the seat the rear shock absorber was mounted longitudinally and horizontally under the engine. Rising rate rear suspension was also in its infancy in 1984, the shock connecting to an aluminium swingarm through a forged aluminium rocker.
Other unique early 1980s features were the adjustable anti-dive on each fork leg and a 16-inch front wheel. The hydraulic anti-dive was virtually useless, only managing to reduce braking feel, while the 16-inch front wheel was another failed introduction from the Grand Prix world. On a bike as light as the 200kg RZ, rolling on a short 1,374mm wheelbase, the small front wheel and fat 120/16-inch tyre provided strange steering. The bike also stood up noticeable under braking into a turn, with a tendency to lock unexpectedly. At least the brakes were up to the task, with opposed piston calipers and vented 267mm discs.
Another strange early 80s inclusion was an 18-inch rear wheel, shod with a high profile 130/80 tyre. It all added up to a confused concoction. The steep steering head angle of 26 degrees, short wheelbase, and small front wheel should have made the RZ agile. Instead Yamaha produced a bike that took more effort to ride in tighter corners than expected, but was exceedingly stable at higher speeds.
The RZ500 was all about Grand Prix fantasy. On the RZ500 you could imagine being Kenny Roberts or Eddie Lawson, the smoky haze from the four exhaust pipes emphasising two-stroke superiority. There wasn’t a four-stroke that could stay with the RZ once it hit the powerband. I have many clear memories of an RZ500 patrolling the Ocean Road in Victoria on a Sunday morning during the 1980s, comfortably annihilating any four-stroke sports bike that dared approach.
Australia’s go-to-guy for classic motorcycle wisdom. Ian has written nearly 45 books on motorcycles that each offer unparalleled insight on the historical and technical development of particular makes and models.