Yamaha XT660R / XT660X Service Manual (2004)

Yamaha introduced the XT660R for the 2004 European model year as a complete renewal of its long-running big-single trail line. Yamaha's 2003 launch release positioned it as the successor to the XT600E, which had served the European market since 1990, and described the new bike as combining city usability, long-range on/off-road versatility and improved high-speed cruising. The redesign brought a new engine, new frame and sharply revised styling while retaining the practical character that had defined Yamaha's XT series since the XT500 era. See Yamaha's official XT660R launch announcement.

The new powerplant was a 660 cm³ liquid-cooled, four-stroke SOHC single with four valves, electronic fuel injection and a 100 × 84 mm bore and stroke. Factory specifications give a 10.0:1 compression ratio, while the five-speed constant-mesh transmission drives the rear wheel by chain. Yamaha also adopted a roller-type rocker-arm valve mechanism and electronic injection as part of the move away from the air-cooled, carbureted XT600E architecture. The result was a fuel-injected 660 cc big-single trail platform designed to deliver useful torque across everyday road speeds while meeting newer emissions requirements.

The XT660R used a diamond-type frame, 21-inch front and 17-inch rear spoke wheels, 225 mm of front suspension travel and 200 mm at the rear, reinforcing its mixed-surface trail role. Its 1,505 mm wheelbase, 865 mm seat height and 181 kg wet weight were paired with a 298 mm front disc and 245 mm rear disc. Yamaha's 2004 specification therefore balanced genuine trail-oriented chassis dimensions with equipment intended for frequent road use and longer-distance travel.

The XT660X was developed from the same mechanical platform as a Supermoto-style road variant. Yamaha's 2003 Tokyo Motor Show material identified it directly as an XT660R variation, using 17-inch road wheels, a 320 mm front disc with a four-piston caliper, shorter suspension travel and altered steering geometry. Despite those chassis differences, both versions share the same 660 cm³ fuel-injected single-cylinder engine and core drivetrain. The platform later also influenced Yamaha's MT-03; Yamaha's 2005 announcement states that the MT-03 engine was based on the XT660R/X unit, showing how the new XT engine architecture extended beyond the original trail and supermoto pair. See Yamaha's 2003 XT660R/XT660X technical presentation.

For related documentation, browse the Yamaha XT660R category or the broader Yamaha catalog. This listing is based specifically on factory publication 5VK1-AE1 for XT660R(S)/XT660X(S) 2004. The title page states First edition, December 2003, and the final wiring diagram is explicitly labeled for the 2004 models. Because the 462-page PDF contains no later model-year supplements, its verified catalog applicability is 2004 only rather than the legacy 2004-2016 range.