Aprilia RS4 125 Service Manual (2011)

Aprilia introduced the RS4 125 in 2011 as a major generational change in its lightweight supersport range. The company had spent almost two decades developing the two-stroke RS 125, but the RS4 moved the 125 class to four-stroke power while keeping the full-size race-replica format. Piaggio Group's official 2011 launch release presented the RS4 as Aprilia's first four-stroke 125 sport motorcycle and linked its styling and technology to the RSV4 superbike programme. The previous two-stroke RS 125 initially remained available alongside the new model, making the transition especially clear.

The new platform used a liquid-cooled 124.2 cm³ single-cylinder four-stroke engine with four valves, twin overhead camshafts and electronic fuel injection. Factory specifications give a 58 × 47 mm bore and stroke, 12.6 ± 0.5:1 compression and a six-speed gearbox with a hand-operated wet multi-plate clutch. Compared with the carbureted two-stroke RS 125, the RS4 represented a fundamental change in engine character, emissions strategy and routine servicing while remaining a four-stroke 125 cc supersport. Aprilia also offered Quick Shift as an accessory, bringing a feature associated with the RSV4 APRC into the entry-level sport category.

The chassis preserved the serious small-sportbike architecture that had long distinguished Aprilia's 125s. A die-cast aluminium dual-beam frame was paired with an upside-down hydraulic fork, direct-mounted rear monoshock and 17-inch alloy wheels. Factory dimensions list a 1,350 mm wheelbase, 837 mm saddle height and 140 kg kerb weight, with a 300 mm front disc and 218 mm rear disc. The full fairing, compact tail and triple-headlamp treatment deliberately echoed the RSV4, while the exhaust was tucked into the lower fairing to strengthen the visual connection with contemporary racing machinery.

The range expanded in 2012 with the RS4 125 Replica. Piaggio Group's official Replica announcement placed the model in the longer RS lineage, noting the commercial success of the earlier two-stroke RS 125 and adding RSV4-inspired race graphics and Aprilia Quick Shift as standard equipment on the Replica. The next major naming and styling step came for model year 2017, when Aprilia introduced a substantially renewed RS 125 MY2017, returning to the historic RS 125 name while retaining the four-stroke, fuel-injected 125 platform and aluminium-frame concept.

This listing corresponds specifically to factory Service Station Manual B043126, copyright 2011, whose electrical documentation is identified as RS4 125 MY2011. It contains full engine, injection, electrical, chassis, suspension, brake, cooling and bodywork procedures. Because the publication does not state applicability through 2012-2016, the catalog is conservatively verified for 2011 only. Related documentation is grouped in the Aprilia RS4 125 manual category.