Yamaha Motor says the YFZ450R and YFZ450X complete its sport ATV lineup for 2011. According to Mike Martinez, Yamaha ATV and Side-by-Side Vehicle Group General Manager, Yamaha started the high-performance 450 sport ATV class with the original YFZ450.
While the YFZ450R and X both feature a long-travel adjustable suspension, a no-weld aluminum with steel hybrid frame, and a fuel-injected engine, there are "subtle differences [that] have a major impact on their performance in different riding situations," says Yamaha. The YFZ450R is a motocross-ready ATV at 48.8 in (1240 mm) wide, making it suitable for wide-open trails, desert terrain, and sand dunes. The YFZ450X is tweaked to be a tight-trail machine at 46.1 in (1170 mm) wide with optimized suspension settings.
Both Yamaha models have five-valve DOHC liquid-cooled single cylinder 449 cm3 engines. Yamaha's electronic fuel injection features a 42-mm (1.6-in) Mikuni throttle body, 12-hole Denso injector system, and a Mitsubishi 32-bit ECU providing for thorough atomization of the fuel for maximum power, improved throttle response, and automatic altitude and temperature adjustment.
The frame is aluminum for reduced weight, though the frame member under the engine is made of tensioned steel for its combination of strength and thinness. That material choice allowed the designers to sit the engine lower overall for improved mass centralization and handling. The aluminum frame is bolted together, rather than welded, for maximum durability. The front frame is noticeably narrow at the A-arm mounting points, dramatically reducing changes in camber as the long A-arms travel through their full range of motion.
The suspension on both YFZ450R and X models comes from the 44-mm (1.7-in) KYB shocks in front that have Kashima coating for smooth operation and impact absorption. The 450R has 9.8 in (250 mm) of wheel travel while the 450X has 9.4 in (240 mm). In the back, the gravity-fed cast aluminum swingarm is matched to a fully adjustable 46-mm (1.8-in) KYB piggyback shock affording the rear wheels 11 in (280 mm) of travel on both models.
Yamaha says it designed its YFZ450R and X models with not just improved power and performance in mind but also comfort and ergonomics for the riders. When the all-new 450R was introduced in 2008, it included the new lighter chassis with a T-shaped seat, flexible side panels, four-position adjustable ProTaper handlebars, and custom-designed Dunlop tires.
Both the ATVs are available in Special Editions models, which feature quick-release fasteners for no-tools installation and removal of the front and rear fenders, a black swingarm, and a dealer-installed GYTR black front grab bar.