2004 Yamaha YZ250

2004 Yamaha YZ250 – The Final Steel-Frame YZ250

The 2004 Yamaha YZ250 was primarily an evolutionary update to Yamaha's established two-stroke motocross platform, but history has given the model particular significance. It became the final steel-framed YZ250 before Yamaha introduced its aluminium-frame generation for 2005. That makes the 2004 machine an interesting endpoint in the development of a chassis and engine combination Yamaha had refined over many seasons.

Power came from the familiar 249cc liquid-cooled two-stroke single with a 66.4 mm bore and 72.0 mm stroke. A Keihin PWK38S carburettor supplied the mixture, while Yamaha's power-valve system helped broaden the engine's usable power delivery. Owners maintaining an original or restored machine can consult the MXOwners carburettor information and replacement options when investigating worn components, jetting or replacement carburettors.

The 2004 chassis retained Yamaha's steel semi-double-cradle construction, combined with an inverted cartridge fork and linkage-type Monocross rear suspension. Approximately 300 mm of front wheel travel and 315 mm at the rear provided the long-travel suspension expected of a competition motocrosser. On surviving examples, worn fork bushings, seals, shock components and linkage bearings can dramatically alter the handling. The MXOwners fork oil level reference can assist owners checking suspension service information.

The YZ250 continued with the established 21-inch front and 19-inch rear motocross wheel combination, using 80/100-21 and 110/90-19 tyres. Owners comparing modern replacements can use the MXOwners motorcycle tyre size guide. Although the 2004 model was not a ground-up redesign, its position as the last steel-frame YZ250 makes it historically distinctive. A year later the aluminium chassis would change the construction of the YZ250 considerably, leaving the 2004 model as the final expression of Yamaha's long-developed steel-frame two-stroke formula.