Aprilia RX 125 / SX 125 Service Manual (2008)

Aprilia presented the RX 125 and SX 125 at EICMA in November 2007 and brought them to market during the first half of 2008. Piaggio Group's official reporting described the pair as high-performance 125 cc motorcycles with distinctive styling, aimed particularly at younger riders. Although they shared a common mechanical base, Aprilia gave them clearly different roles: RX was the enduro version for mixed-surface and off-road use, while SX translated the same concept into a road-oriented supermoto with smaller wheels and wider sport tyres.

The 2008 machines were built around a liquid-cooled 124.82 cm³ single-cylinder two-stroke with reed-valve induction and separate automatic oil injection. Factory specifications give a 54 × 54.5 mm bore and stroke, 12.5 ± 0.5:1 compression and Dell'Orto VHST 28 CD carburetion. Drive passes through a hand-operated wet multi-disc clutch and six-speed gearbox. Aprilia supplied different chain gearing for RX and SX and also documented 11 kW and full-power configurations, with the RAVE exhaust-valve system associated with the latter. This combination made the pair a distinctive two-stroke 125 enduro and supermoto platform at a time when emissions rules were steadily reducing the number of road-legal two-stroke motorcycles.

The chassis layout reinforced the different personalities without changing the basic structure. Both use a high-strength steel double-cradle frame, 40 mm upside-down fork with 260 mm travel, gas rear monoshock with 265 mm travel, a 1,480 mm wheelbase and disc brakes measuring 260 mm front and 220 mm rear. SX uses 17-inch wheels with 110/70 front and 150/60 rear road tyres and an 870 mm saddle height. RX instead uses traditional enduro dimensions, with a 21-inch front, 18-inch rear, 90/90 and 120/90 tyres, and a taller 925 mm saddle. Both are listed at 126 kg kerb weight with a full tank.

The RX/SX concept survived beyond this two-stroke generation, but its engineering changed substantially. At EICMA 2017 Piaggio introduced a new 2018 RX and SX 125 generation using a Euro 4 liquid-cooled four-stroke single, updated chassis equipment and ABS with anti-roll-over control. The basic division remained intact: SX continued as the 17-inch supermoto and RX as the 21/18-inch enduro. Aprilia again refreshed the family for 2021 with a Euro 5 engine, updated electronics and revised styling, demonstrating that the paired enduro/supermoto formula had become a durable part of its entry-level range.

This listing is based on Service Station Manual 854196, copyright 2008, which covers both models and includes scheduled maintenance, electrical diagnosis and wiring, complete two-stroke engine and gearbox overhaul, carburettor service, suspension, chassis, cooling and bodywork procedures. The source contains no application table or later-year update establishing 2009-2013 compatibility, so catalog coverage remains restricted to 2008. Related documentation is grouped in the RX 125 category and SX 125 category.