Having completed our MX-Periment with mixed results and reviews (September/October and November/December 2010 issues), we decided to let pro ATV racer Keith Little attack our YFZ450R completely on his own. What he came back with was both eye opening in its performance and stellar in its simplicity.
The Yamaha YFZ450R, like many of its competitors, has been touted as a race-ready machine, and like the others it pretty much delivers for most amateur racing classes. While we're not pro-caliber riders by any stretch of the imagination, we've somehow developed pro-caliber tastes, which is why we can't seem to leave well enough alone when it comes to our ATVs. Truthfully, racing at the pro level isn't realistic for an "off the showroom" unit, so we enlisted Keith's help in turning our stock Yamaha into a true pro-level competitor.
The YFZ450R does everything pretty well; it's light, nimble and quick enough in stock trim to keep most folks happy. Lucky for you, we're not like most folks, and our incessant need to extract every ounce of potential from a machine is a quality we share with Keith. In stock trim, the YFZ is a thing of beauty and just yearns for MX action. Measuring in at 48.8 inches wide, it's right where you want to be for MX, and with a "wet weight" of 405 pounds, it's close to ideal fighting weight as well. The frame is aluminum except for the lower frame rails (which are steel) and is bolted together as opposed to welded, which gives it a somewhat rigid feel but theoretically makes it stronger. The fuel-injected, 449cc, liquid-cooled, DOHC, titanium five-valve motor is quick enough for most local racers to rip holeshots with nothing more than a bolt-on exhaust system. Suspension-wise, the front KYB shocks' 9.8 inches of travel is capable of handling most of what the average rider might encounter on the track. The rear KYB shock offers up an impressive 11 inches of travel and is high/low-speed compression, rebound and preload adjustable (which goes for the front shocks as well). "It's pretty awesome in stock trim; I rode it for a few weeks before installing any aftermarket parts. I knew I could clear every jump on our track without a problem. I'm not saying it wouldn't have been sketchy, just that it could be done. I really couldn't wait to rip [the YFZ] apart and see where I could make it better," Little stated.
The KLR Treatment
It's almost harder to overhaul something that's not necessarily broken than a really unusable turd, which is why we were curious as to how far Keith would go on this build. In reality, we were surprised by how little (no pun intended) Keith actually did. Not to say the YFZ hadn't been gone through with a fine-tooth comb, but rather how much of the OEM equipment met Keith's stringent standards. At a glance, the machine looked fairly conservative and more "showroom" than most of the "works-looking" machines in the KLR stable.