(54Ko jpg)

The Standard RDLC

Photos courtesy of Yamaha and MJ (#643 & #656)

Inspired by the YZR500 factory racer ridden by Roberts (14Ko jpg) during the 1983 Grand Prix season, the RD500 was the closest thing to a Grand Prix bike. And in 1984, you could get your hands on the twin-crank V4 bike. Three different versions of the red & white bike were available worldwide.

The RD500LC, which comes equipped with Michelin tires, was sold in France and in Europe. In Australia, New Zealand and Canada, the bike was sold named RZ500 (39Ko jpg) and had the same equipment than in European version. Japan received a limited edition RZV500R, replete with a lighter aluminium frame (the others used steel) and other goodies. But the engine power was tuned down to 64 Hp.
The RD500 or RZ500 were never sold legaly in the United States due to Environmental Protection Agency. Does a RD500 pollute!!!!

The frame is a mild steel box-section rails in a perimeter layout. The rear shock, which on most bikes is in an upright position under the seat, had to be placed horizontally under the engine. The under-seat area is packed full of the upper cylinders' exhaust cambers, the battery and the YPVS servo motor. This positioning adds the benefit of consolidating mass in order to improve the RD's center of gravity and to make the bike flickable. The rear of the shock connects to an extruded aluminum swingarm via a forged-aluminum rocker; a small forged link attached to the rocker's center pivot positions it relative to the frame. A few other chassis features incorporated on the 500 were innovative back in 1984. For instance, the bike's non-adjustable forks use spindly 37mm stanchion tubes, and the front of each lower fork leg carries an adjustable anti-dive valve. The twin disc brakes up front, as well as the rear disc, are ventilated, an experiment Yamaha tried on several of it's street bikes in the mid Eighties (FJ1100...). 

The 1983 OW -70 bike used a 50-degree, twin-crank V-four motor equipped with Yamaha' YPVS exhaust power valves. The RD utilized reed valves to achieve a broader, more street-oriented power band. But, again due to limited space in the V, the reed valves used two different intake arrangements. The lower cylinders were fed through crankcase reeds; the upper pair used cylinder reeds (34Ko jpg), with 90 degree intake manifolds connecting each reed block to it's side-mounted carburetor.
The lower exhaust pipes exit in traditional two-stroke fashion, but the upper pipes cross over each other just aft of the exhaust ports to help maintain proper tuned length without having the pipes protrude out of the back of the bike.

The dual primary drives were geared directly to the clutch, while the front crankshaft also spun a counter balancer that is mounted deep inside the "V" between the two cranks. The counter balancer, unusual on a two-stroke, helped dampen engine vibration. A servo-controlled YPVS system -similar to the system used on Yamaha's RD350 - bolstered low and mid-range power, and let gasses flow into four individual expansion chambers.


Manufacturer: Yamaha
Model:  RD500LC
Price: 42000 in 1984
Engine: Two-stroke, liquid-cooled,
        reed-valved 50-degree V4
Bore x stroke: 56.4 x 50.0 mm
Displacement:  499cc
Carburetion:  (4) 26mm Mikuni
Transmission:  6-speed
Wheelbase: 1375 mm
Seat height: 780 mm
Fuel capacity: 22 l
Claimed dry weight: 177 Kg

Photos courtesy of Yamaha and Moto Journal (#643 & #656)

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