Hyosung RX125 Service Manual (1999)

Hyosung began motorcycle production in 1978 through technical cooperation with Suzuki and moved steadily toward its own designs during the following decade. Hyosung's corporate history notes the establishment of motorcycle manufacturing in 1978, the Suzuki relationship and the move to independently developed products by 1987. A later company timeline published by Motorrad places development of the RX125 Off-Road in 1998, alongside a broader expansion of Hyosung's own 125 cc range. Hyosung's corporate history and Motorrad's Hyosung timeline provide that background.

The RX125 was conceived as a lightweight on/off-road machine rather than a street-only commuter. The early factory specification used a 124.5 cm³ single-cylinder SOHC four-stroke with a 57 × 48.8 mm bore and stroke, PD18F carburetor, wet-sump lubrication and a five-speed constant-mesh gearbox. Electric starting was backed up by a kick starter, while 21-inch front and 18-inch rear wheels, 295 mm ground clearance and 250 mm of front-fork travel gave the motorcycle genuine rough-road proportions. A front disc and rear drum kept the braking system simple and appropriate to the class.

Those specifications placed the RX125 squarely in the 125 cc dual-purpose motorcycle category that was important for novice riders and practical transport in markets where small-capacity licensing and operating costs mattered. The 1999 specification weighed 125 kg dry, carried 9 litres of fuel and used a 1,425 mm wheelbase. Its chassis combined a telescopic fork with a swingarm rear suspension, while the engine used battery CDI ignition and chain final drive. The result was a straightforward, repairable design with enough off-road-oriented chassis geometry to distinguish it from Hyosung's roadgoing 125s.

The RX125 name continued into later export markets, but the motorcycle did not remain technically static. A 2005 road test by The Irish Times described a later RX125 with an oil/air-cooled four-valve engine, 41 mm upside-down fork, 116 kg dry weight and an 850 mm seat height. Those differences from the 1999 factory specification show meaningful development within the model's life and are a reason not to assume that one early workshop manual applies unchanged to every later RX125.

This listing is therefore tied to the dated factory publication rather than the previous broad 1998-2009 catalog range. The source is Hyosung Motors & Machinery Inc. Service Manual No. 99000-97100, explicitly marked “1st Ed. Feb. 1999,” and its foreword states that it covers inspection, service and overhaul of the RX 125. Because the publication itself states no broader model-year applicability, catalog coverage is conservatively limited to 1999. Related factory publications are grouped in the Hyosung RX125 manual catalog.