Introduction

Aprilia - RS 50 (1999, ZD4TSJ)

The Aprilia RS 50 (model year 1999, ZD4TSJ) is a fully-faired 50 cc motorcycle with a supersport design. It was developed specifically for young riders who wanted a real racing feel despite being in the 50 cc category.
With its aggressive styling, high-quality chassis components and powerful engine, the RS 50 set standards in its class – both in looks and performance.

Model history

In 1999, Aprilia introduced the ZD4TSJ model as an updated version of the popular RS 50. Built at the Noale factory, it benefitted from Aprilia's Grand Prix racing expertise.
The aim was to offer a true sportsbike character within the legal limits of 50 cc vehicles, while delivering maximum riding enjoyment.
The RS series quickly became iconic among sporty 50 cc machines and paved the way for future lightweight sport bikes.

Technical details

The Aprilia RS 50 (ZD4TSJ) is powered by a liquid-cooled single-cylinder two-stroke engine with 49 cc displacement. The engine is a Minarelli AM6 unit known for its high revs and tuning potential.
Restricted output was around 1.5–1.8 kW, while derestricted setups could deliver up to 6.8 hp, depending on exhaust and configuration.
Power is transmitted via a 6-speed manual gearbox that allows precise, sporty shifting.
The chassis uses a twin-spar aluminium frame, offering low weight and excellent torsional stiffness.

Chassis and brakes

At the front, the RS 50 features an upside-down telescopic fork; at the rear, a mono shock swingarm – both tuned for sporty riding.
Braking is handled by a 280 mm perforated disc up front and a 220 mm disc at the rear – both hydraulically operated.
Weighing in at around 96 kg dry and with a sporty riding position, the RS 50 offers sharp and agile handling.
Tyre sizes are 100/80-17 front and 130/70-17 rear – unusually large for a 50 cc motorcycle.

Design and features

Visually, the RS 50 takes strong cues from Aprilia’s larger race bikes – featuring twin headlights, full fairing, racing graphics and a sporty seat.
The analogue dashboard includes rev counter, speedometer and temperature gauge, and the fuel tank holds around 12 litres.
Various factory decal kits and racing parts were available to further personalise the bike.

Colour variants

In 1999, the RS 50 was available in several striking paint schemes – including black/red, Repsol-style racing colours and silver designs with bold graphics.
Many units were further customised by their owners, including exhaust swaps, new liveries and levers.
Official special editions are not documented for the ZD4TSJ, but customisation was already central to the RS 50 scene at the time.