Hyosung GV650 Aquila / GT650 Comet FI Service Manual Supplement (2009)

Hyosung developed its 650 cc V-twin family during the early 2000s as the Korean manufacturer's step into the international middleweight motorcycle market. After making smaller Comet roadsters, it introduced the 647 cc GT650 naked road bike in 2004. A contemporary report on its arrival records the model's international expansion. The engine was a liquid-cooled, double-overhead-cam 90-degree V-twin with four valves per cylinder; its 81.5 mm bore and 62.0 mm stroke became the foundation of a broader group of motorcycles. This was an important platform change, taking the company from mainly small-capacity machines into a segment populated by larger Japanese and European competitors.

Hyosung expanded the Comet lineage with GT650, GT650S and GT650R models that shared the same basic V-twin engine but offered different bodywork and uses. The original GT650 was a naked roadster, the GT650S added a half fairing to improve wind protection, and the GT650R adopted a full fairing with a more sporting appearance. These three machines retained a six-speed constant-mesh gearbox and chain final drive. Their differing styling, seating arrangements and touring emphasis allowed the company to address multiple groups of road riders while keeping much of the engine and mechanical platform in common.

Another important branch was the GV650 Aquila, developed around the same 647 cc engine family but configured as a low-slung power cruiser. The Aquila used a longer wheelbase, cruiser ergonomics and an 18-inch front wheel, distinguishing it from the shorter-wheelbase Comet machines. It also employed a five-speed transmission and belt final drive instead of the Comet's six-speed chain-driven arrangement. Introduced in the middle of the decade, the GV650 broadened Hyosung's cruiser range beyond its earlier small-displacement Aquila models and gave the company a distinctive performance-oriented cruiser. The Hyosung owners' historical timeline documents these developments and the changing model range.

Early 650-series motorcycles used carburetors, but increasingly stringent emissions rules drove a transition to electronic injection from the late 2000s. The first-generation fuel-injected 650 V-twin family added ECU-controlled fuel metering, throttle and intake-pressure sensing, oxygen feedback and electronic fault diagnosis. By 2009, the S&T Motors technical documentation reflected refinements to this system, including updated electrical connections, a roll-over switch and revised diagnostic thresholds. Alongside the fueling transition, the GT650i models received revisions to their instrumentation, bodywork and brakes during the period. The overall evolution retained the established liquid-cooled engine architecture while altering the servicing and troubleshooting required for modern electronic fuel control.

The 2009 fuel-injected Aquila and Comet machines formed an intermediate phase between Hyosung's original carbureted models and later revisions such as the GV650 Pro cruiser. Their history is one of a shared mechanical platform adapted for multiple motorcycle styles, followed by a gradual change in engine management rather than a replacement of the fundamental V-twin design. Related titles covering the earlier models are listed in the Hyosung service manual catalog. S&T Motors publication 99000-51320 is the June 2009 EI-specific supplement; its foreword references older carbureted-model workshop books for procedures it does not reproduce. The date identifies this edition and does not by itself establish applicability to every production year of the EFI range.