Its 1998 ancestor was the motorcycle that allowed four-strokes to reclaim their rule over off-road racing. Twenty years later Yamaha reintroduces the WR450F, with a new frame and engine along with a host of changes and upgrades, such as the ability to tune the engine wirelessly via a smartphone app.

When Yamaha first rolled out the YZ400F motocross bike, it did more than just build a new weapon for the off-road racing scene; its four-stroke single cylinder engine ignited a revolution.

Starting from the early 1960s, two-strokes had gradually ousted four-strokes from the highest levels of off-road racing and their reign remained uncontested until 1998.

That was the year when Yamaha introduced its 400-cc thumper, with an engine that used contemporary superbike technology in order to match every advantage the two-strokes could rely on, other than simpler maintenance. It would rev higher than any four-stroke single had ever before – climbing well over 11,000 rpm – and produce usable power all through the spectrum, effectively outgunning the narrow power band of the two-strokes.

By 2002 the FIM had redesigned the world championship's classes to include a new generation of four-strokes, coming from several manufacturers that followed Yamaha's initiative. This was about the same time that MotoGP took a similar turn with the introduction of the 990 four-strokes.

Yamaha proceeded to introduce an enduro/cross-country version of the YZ the next year, the WR400F. It proved to be instantly successful and, over six model generations, it grew to 426 and then 450 cc, got fuel injection, titanium valves and aluminum frame.

The latest model change signified an important turning point, when in 2010 Yamaha redesigned the YZ450F with an uncommon rearward slanted and reversed cylinder; the exhausts exit directly from the back of the cylinder and the fuel injection feeds the motor from the front, while the head changed to the typical four-valve setup. It took six years for this engine to arrive at the WR model, which was formally introduced in 2016.

Last year Yamaha renovated the YZ450F with new engine, frame and electronics and now these updates filter through to the 2019 WR450F. Most of these are shared with the special YZ450FX version, which is actually the motocross model fine-tuned for cross-country use.

The slanted and reversed cylinder architecture remains unchanged, but Yamaha suggests that the engine is brand new, designed to produce more power over a broad rev range. In order to adapt the engine to its new role, it is equipped with a new clutch and new intake and exhaust systems, as well as the appropriate fuel injection and ignition mappings.

One of the most important innovations of the 2018 YZ450F was the incorporation of a Wi-Fi system that allowed the rider to tinker with engine settings easily through the Power Tuner smartphone app. It was the first of its kind for a motocross bike.

This kit is now available with the new WR450F as part of the optional race kit that includes a communication control unit for wireless connectivity. The rider can make fueling and ignition timing changes, view diagnostics, as well as record, upload and share race data straight from a smart device.

One more feature carried over straight from the latest motocross model is a selector button on the handlebars, giving the rider instant access to two different engine maps.

The aluminum twin-spar or bilateral beam frame, as Yamaha calls it, is slimmer and lighter, incorporating several changes compared to the YZ frame for more traction and precise handling. To this end, the seat is also redesigned to be slimmer in the front and a tad lower in the middle and rear, allowing for easier movement of the body while riding.

The suspension of the WR450F is based on the corresponding YZ units, revalved and resprung for enduro use.

Other notable features of the WR450F include a 7.9 liter (2.1 gal) fuel tank, up from the 7.5 l (2 gal) of the previous model. Finally, the styling is revamped with a new headlight design, new radiator shrouds and fresh graphics.

The 2019 WR450F will be available at European dealerships starting in October, while in the US it should arrive in January 2019. It should be noted that in the European Union it will not be road legal as it is not homologated for the Euro 4 norms.

Source: Yamaha

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