The RS4 125 arrived in 2011 as Aprilia's first four-stroke 125 sports bike, taking over from the long-running two-stroke RS 125.
| MODEL | APRILIA RS4 125 2011 |
| Year | 2011 |
| Engine Type | Four-stroke, single cylinder, DOHC, 4 valves |
| Displacement / Capacity | 124.8 cc / 7.6 cu in |
| Bore X Stroke | 58 x 47 mm / 2.3 x 1.9 in |
| Compression Ratio | 12.5:1 |
| Cooling System | Liquid cooled |
| Max Power | 11.7 kW / 16 hp @ 10500 rpm |
| Max Torque | 11 Nm / 8.1 lb-ft @ 8500 rpm |
| Ignition | Electronic, CDI |
| Induction | Electronic fuel injection, Magneti Marelli MIU G3, 32 mm throttle body |
| Start System | Electric |
| TRANSMISSION SPECS | |
| Lubrication | Wet sump |
| Gear Box | 6-speed |
| Clutch | Wet multi-plate (oil bath) |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | Aluminium perimeter frame with die-cast spars |
| Front Suspension | 41 mm upside-down fork, 110 mm / 4.3 in travel |
| Rear Suspension | Asymmetric swingarm with monoshock, 130 mm / 5.1 in travel |
| Front Brakes | Single 300 mm stainless steel disc, radial 4-piston caliper |
| Rear Brakes | Single 218 mm stainless steel disc, single-piston caliper |
| DIMENSION SPECS | |
| Overall Length | 1953 mm / 76.9 in |
| Overall Width | 740 mm / 29.1 in |
| Overall Height | 1138 mm / 44.8 in |
| Seat Height | 820 mm / 32.3 in |
| Wheelbase | 1350 mm / 53.1 in |
| Ground Clearance | — |
| Dry Weight | 120 kg / 265 lbs |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | 110/80-17 |
| Rear Tyre | 130/70-17 |
| FUEL SYSTEM | |
| Fuel Capacity | 14.5 Litres / 3.8 US gal |
| Fuel Consumption | — |
| Top Speed | 110 km/h / 68 mph |
The RS4 125 arrived in 2011 as Aprilia's first four-stroke 125 sports bike, taking over from the long-running two-stroke RS 125. Its fuel-injected, liquid-cooled DOHC single is tuned to the A1 learner-licence power cap, and it wears bodywork styled after the RSV4 superbike, with the triple headlight and an exhaust tucked into the belly pan. The aluminium perimeter frame, 41 mm upside-down fork and radial four-piston front brake gave it a chassis well above the usual learner-bike standard, and a quickshifter and single-seat cowl were offered as accessories.
