After the port is closed and the air is compressed by the piston, gasoline is injected by an atomizer like a spray nozzle mixed with and propelled by the highly compressed air, into the main combustion chamber where, after the injection port closes, and the piston is still rising, it is ignited in the compressed main charge of air.

The system uses a crank-driven air compressor to deliver air to the cylinder head at a pressure of 5 bars (500 kPa 73 psi), thereby avoiding the use of carburation the cylinder walls are not wet with gasoline, only with lubricating oil. The SR50 DITECH uses the Synerject gasoline direct injection (GDI) system developed jointly by the Orbital Corporation and Siemens AG. The powerful engines allow reaching very high speeds for a scooter, the SR50 can reach 90 km/h in its standard configuration after being derestricted. The current model uses a Dell'Orto waterbottle. The DiTech model used an injection engine, with technology from Orbital. It conforms to EURO 3 emission standards. The SR50 has used a variety of engines, sourced from Morini, Piaggio and Minarelli. The digital instrument panel gives readings for speed, clock, odometer, trip counter, fuel level, coolant temperature and battery voltage.

The performance-oriented suspension, tires, and engine are consistent with its styling.

Aprilia claims several firsts for the SR50 in the scooter market, including 13 inch wheels, liquid cooling, double disc braking, and a direct injection engine. Introduced in 1992, more than 800,000 units have been sold, bucking the trend for less use of two-stroke engines.

Aprilia sr50 street main jet