The Yamaha WR426F was a dirt bike that generated interest in rapidly improving four-stroke technology. The idea that a four-stroke thumper could be a competitive machine, and not make for a grossly overweight bike, pleased many off-road enthusiasts and had everyone thinking; not having to premix fuel for a two-stroke engine was something to cheer for. The '03 WR450F builds on the success of Yamaha's proven four-stroke platform by adding more power, taking away some weight, and becoming easier to ride than previous incarnations.
The WR450's powerplant grew 24ccs from 449ccs. The DOHC, five-valve, liquid-cooled, twin-cam motor is fed by a 39mm Keihin carburetor and titanium valves. The Keihin FCR carb is equipped with a throttle-position sensor designed to enhance throttle response over a wide range of operating conditions. To help start the bike once the motor is warmed up, the carburetor features an all-new hot-start system with a handlebar-mounted lever. The positioning of the lever is a welcome change that simplifies operation if the bike stalls.
A three-bar shifting mechanism makes speed shifting the WR quick, precise, and easy. Through long straightaways, or when short-shifting the bike out of a tight turn, the wide-ratio, five-speed transmission and multiplate wet clutch work fluidly. In line with the easy-to-operate theme is a works-style adjustable clutch perched onboard. The perch can be adjusted without tools to improve its feel and response.
The WR450F's suspension also received its fair share of attention during the bike's redesign. An all-new swing arm is tapered and more rigid than previous models. The rear shock's high- and low-speed compression settings have been improved to smooth out the ride through tight, punishing trail sections.
The brake system shed some weight with all-new master cylinders and calipers. The front brakes clamp onto a 250mm floating disc, while the rear calipers squeeze a 245mm disc and deliver strong and predictable stopping power. The Excel rims and lightweight hubs also shed precious pounds and are combined with very aggressive Dunlop tires.
Maintaining the WR450F is a simple operation thanks to the numerous features designed to allow access to pertinent areas of the bike. An aluminum subframe is present and allows access to the oil and air filters. The air-filter assembly doesn't even require handtools for removal. The subframe narrowed this nimble machine a bit and helps when navigating tight trail sections.
The '03 Yamaha WR450F is available in Team Yamaha Blue and White colors and looks the part of a serious off-road machine. Thankfully, this thumper also has the performance to back up its racy good looks. With an abundance of new power, easier operation, and a slimmer figure, this bike is ready to rip up your riding area. Check it out at your local Yamaha dealer.