Best Dirtbike of the Year Winner: Yamaha YZ450F
Yamaha’s reverse incline-motored YZ450F is kind of like the legendary rock band Kiss. Just like it took hard rock’s masked marauders five years and four albums to become overnight sensations, the YZ450F finally came Alive! in 2015 by hitting upon the right combination of engine performance, chassis rigidity and suspension compliance to make it a winner.
It seemed as if Yamaha engineers left no stone unturned in their quest to fulfill the potential of the latest-generation YZ450F, which was completely redesigned for 2014. For 2015, the big blue machine received relatively minor updates, but the simplest improvement may have made the most impact: The YZ450F received new ECU settings designed to smooth out the 450’s low-rpm throttle response as well as give it more low-end torque and better top-end overrev than the 2014. The ECU change turns the YZ450F into a snappier performer but also makes it easier to ride by virtue of its ability to hold a gear longer between shifts. This endearing trait gives the YZ450F the best of both worlds – it’s a 450cc motocrosser that makes fire-breathing, pro-level power that can be equally enjoyed by less-skilled riders. What more could one ask for?
How about a really well-behaved bilateral beam chassis that is comfortable and compliant? The YZ450F’s thinner motor mounts and suspension changes help to deliver a less rigid feel through the bars, less harshness, than the previous model, yet the YZ’s KYB suspension can still swallow up supercross-style whoops and heavy landings with ease. A super-slim ergonomic layout and feel also hide its 248.5 lbs. well, making it seem smaller and lighter than it really is.
The 450cc motocross class may be one of the toughest categories to dominate in all of motorcycling, but for 2015 the Yamaha YZ450F was the bike we’d choose to rock and roll all night and party every day at our local moto haunts.
Honorable Mention: 2015 Yamaha YZ250FX
Honda’s CRF450R deserves a shout-out for its convenient Engine Mode Select system, which allows the rider to access different EFI/ignition maps by pressing a button mounted on the handlebar, rather than the typical hassle of unplugging swappable modules in the pits. But it’s Yamaha’s new crossbreed, the YZ250FX, that takes our Honorable Mention award.
Yamaha’s all-new YZ250F earned our MOBO honors in last year’s dirtbike category because it set a new benchmark in 250cc power and handling that may be difficult for its competition to surpass without complete redesigns of their own. So, Yamaha figured, why not take all of the great aspects of the YZ250F and re-tune them to produce an off-road racing model that lives up to the YZ250F’s performance reputation? The“tuning fork” company did just that, giving its venerable WR250F a new off-road racing stablemate with a decidedly more aggressive personality, the Yamaha YZ250FX.
The YZ250FX’s engine is almost a spitting image of the YZ250F’s fuel-injected, DOHC, liquid-cooled four-stroke engine. The FX boasts the same 77.0 x 53.6mm bore and stroke and 13.5:1 compression ratio of the YZ, and even its camshafts profiles are identical. Its only differences include convenient electric start, and an ECU that is more suited to off-road racing than motocross. Yamaha also gave the FX a more off-road-worthy six-speed transmission with steeper first and second gear ratios for crawling over rocks and taller fourth through sixth gear ratios for Mach speeds in wide-open terrain. The YZ250FX’s bilateral beam aluminum chassis is identical to the YZ250F’s, although the damping specs for its 48mm KYB SSS fork and piggyback shock are revised for off-road use.
The end result is an off-road motorcycle that is capable of winning races right out of the crate. The YZ250FX delivers the dirt-scorching power and feather-light handling of the YZ250F in a more flexible package for the off-road and desert racing crowd. Granted, the 250FX is sold as a closed-course-only racer, but in most states all it takes to fix that is the addition of a USFS-approved spark arrestor. A lot of folks seem to have caught onto the FX’s potential, as it has become the best-selling 250cc machine in the cross-country off-road sub-category in 2015.