Development
With
the success in the early 1980s of Kenny Roberts
and the Yamaha YZR500 in Grand Prix motorcycle
racing Yamaha realised that a road going replica
of their 500 cc racing machine would sell
well. Using the similar technology of the
smaller RD series of two stroke motorcycles
the RD500LC was launched in 1984 to an enthusiastic
riding public.
Engine
The RD500LC uses a 50-degree, twin-crankshaft
V4 engine layout. Linked Yamaha YPVS exhaust
power valves are controlled by a single electronic
unit and servo motor and are designed to give
a broader power band. The engine also featured
intake reed valves unlike the YZR500 racer
which used rotary disc valve induction. The
reed valves used two different intake arrangements,
the lower cylinders were fed through crankcase
mounted reeds; the upper pair used cylinder
barrel mounted reeds. The carburettors are
side mounted in pairs and feed each cylinder
through 90 degree intake manifold. The lower
expansion chambers exit normally but the upper
pipes cross over each other just behind the
exhaust ports to maintain the correct tuned
length. The dual crankshafts are geared directly
to the clutch, while the front crankshaft
also drives a counter balancer shaft mounted
between the two crankshafts. The counter balance
shaft, unusual on a two-stroke, assists with
dampening engine vibrations. The engine is
cooled by thermostatically controlled liquid
cooling, an auxiliary electric fan mounted
behind the radiator cuts in at high temperatures
(e.g. when stationary in traffic). Lubrication
is by direct injection in to the inlet manifolds
using Yamaha's 'Autolube' pump system, normally
controlled in other two-stroke engines by
throttle position the engine oil pump is controlled
by the YPVS servo motor ensuring that the
oil supply is not shut off at high engine
revolutions.
Transmission
The RD500LC uses a six speed sequential
close ratio gearbox, the gear shafts
are removable from the right side of
the engine without the need to split
the crankcases. The clutch is of the
wet, multiple-disc coil spring type
and is cable operated. Unusually for
a two stroke the gears are lubricated
by a separate crankshaft driven troichoid
oil pump. Final drive is by O-ring chain
and sprockets.
Chassis
The frame of the RD500LC is manufactured
from mild steel box-section and uses a perimeter
layout. The rear shock absorber is unusually
placed horizontally under the engine and uses
the lower crankcase as a mounting point. The
under-seat area is occupied by the upper cylinder
exhaust chambers, the battery and the YPVS
servo motor. The rear of the shock absorber
connects to an extruded aluminium alloy swinging
arm via several forged aluminium rocker arms.
An unusually small diameter 16" wheel is held
between 37 mm (1.5 in) spring and
oil damped forks
which featured adjustable anti-dive units.
The RD500LC used twin ventilated disc brakes
for the front wheel with a single ventilated
disc at the rear. A solo seat cowl is provided
to cover the pillion seat when not in use.
Electrical system
The RD500LC features a standard 12 volt
electrical system. Yamaha's self cancelling
indicator unit is used and a variable resistance
gauging system is used to monitor two-stroke
oil tank contents with associated warning
lights. Nippondenso Capacitor Discharge
Ignition (CDI) is used in conjunction with
two coils.
RZV500R
The RZV500R was designed exclusively for
the Japanese home market although many have
been exported privately. The RZV500R features
upgraded parts not found on the standard RD500LC.
A major difference is the hand-welded aluminium
frame, which is significantly lighter than
the steel version used on standard models.
The front brake lines are braided stainless
steel instead of rubber coated, and the front
forks are air assisted with rebound damping
adjustment. The rear brake and gear levers
are cast from aluminium, as are the clip-on
type handle bars. These chassis modifications
added up to a weight saving of 20 lb
(9.1 kg). The engine was detuned to 64 hp
(48 kW) to comply with Japanese legislation,
this was achieved by restricting the internal
diameter of the exhaust pipes.
Although short lived in the UK enough RD500's
were sold to make them a reasonably common
site on the roads at that time. The RG 500
stole the thunder out of the RD as it was
imported with an alloy frame and was a little
faster and a slightly better bike. But the
brakes wre still crap and the Suz anti dive
was just as slopy as the RD , so it realy
all came down to looks, and the RD500YPVS
wins hands down there.
Yamaha RD500 LC Info;
- Introduced : June 1984 ......... ....
............. .Discontinued : February 1987
- Frame numbers : 84 onwords 47X-000101
Engine numberes : 85 onwards 1GE- 000101
- Colours : Silky white & Stormy red
- Bore and stroke : 56.6mm X 50mm
- Engine type : V4 500
- Power : 79bhp
- Gears : 6
- Wheels : 16-inch front and 18-inch rear
- fuel capacity : 4.8 gallons
- Speed : 135 mph
- Weight : 392 lbs
- MPG : 35 ish.
