Aprilia RS125 RS4 125 2017-2022 Service Manual

MCN's own review sums up the appeal in one line: it's "the best looking one on the market," especially in MotoGP Replica trim, "the stuff of teenage dreams." Confusingly for shoppers, this generation dropped the "RS4" name in most markets in favor of simply "RS125" (though the RS4 badge stuck around in some regions), while retaining the exact mechanical lineage: the 2017 model replaced the 2011-2016 RS4 125, which itself had replaced the beloved two-stroke RS125 that ran from 1992 to 2012.

Power comes from a 124.2cc liquid-cooled single, DOHC with 4 valves and electronic fuel injection, delivering a claimed 15 hp at 10,500 rpm and roughly 8 lb-ft of torque at 8,250 rpm through a 6-speed gearbox with wet multi-disc clutch and optional quick-shift system (standard on the GP Replica trim) that cuts ignition briefly for clutchless upshifts. A factory race kit can bump output to a claimed 25 hp for track use. The RSV4-inspired aluminum perimeter frame and 40mm inverted forks give the RS125 genuinely premium chassis hardware for the class — MCN's review specifically called out the high-spec aluminum frame, inverted forks, and radial front brake with ABS as standouts against rivals like the KTM RC125 and Yamaha YZF-R125.

2021 brought a genuine mid-cycle update: restyled front bodywork, fully digital instruments, a wider 140-section rear tire, full-LED headlights, Euro 5 compliance, and dual-channel ABS. The engine itself was reworked with a new cylinder head, redesigned combustion chamber, revised intake and exhaust ducts, new camshafts, and an iridium spark plug, alongside a repositioned throttle body and new exhaust system. Dry weight sits around 129kg (284 lbs), with a 32-inch seat height and 14.5-litre fuel tank.