2008 Kawasaki KFX450R ATV Test

January 9, 2008
By Billy Bartels
the KFX has jumped into the sport-quad market kicking and spitting all over the established competition.
Kawasaki is the final Japanese manufacturer to join the fray, but now that it has the KFX has jumped into the sport-quad market kicking and spitting all over the established competition.

The world of high-performance sport ATVs is a quickly evolving one. Just four years ago there were exactly zero machines that would qualify as anything more than an inspired trail rider by today’s standards. In the intervening years, Yamaha released their seminal YFZ450, Honda the TRX450R, and Suzuki the very-nearly race-ready LTZ450R. Kawasaki came to the fray a little late with its early-release 2008 KFX450R, which brings a combination of race- and trail-ready features to the mix.

Kawasaki’s entry into the ultra-high-performance quad wars is a fuel-injected motocross-derived 450cc 4-stroke powerplant which is as close to race-ready as a production quad has ever been. So yeah, you’ve heard that before, but the KFX delivers some unique twists to a storyline that has been played out in a variety of ways in the past few years. Unlike motocross-specific machines that are separated by very small differences (necessitated by the need to win races at all costs), ATVs – with or without racing intent – are primarily designed as trail machines first and true racers second, so every manufacturer brings it’s own flavor to the mix.

Kawasaki, while committed to making a high-performance quad, seems to be determined to capitalize on the crossover appeal of the KFX rather than focusing it narrowly as a race-only platform. A light and rigid aluminum frame is the centerpiece, and is joined by modular/removable fenders and lights, a reverse gear, and a fat competition-grade Renthal handlebar, all industry firsts (or near-firsts) in this class; but all triangulated to appeal both to the racer and the weekend warrior. Coming to the party a little later means there’re no gaffes like Honda’s kickstart-only TRX, Yamaha’s heavy-throttled and harshly suspended YFZ, or even Suzuki’s too-wide-for-the-woods LTZ.

Clearly the trickest component on the KFX450R is the chassis which plays a huge role in the bike’s tank-empty weight of 384 pounds. The frame and swingarm are both formed from cast and precision-welded aluminum pieces for maximum rigidity and minimum weight. This design will benefit both racers and off-road enthusiasts, as less weight and more predictable handling is always a good thing. The double-cradle design is fairly conventional, but is strengthened in key places to reduce or eliminate the need for gusseting (as is often the case on other quads in race applications). At the front there is a single box-section lower member that allows for longer A-arms while retaining a narrow width between the wheels, which in turn creates more, and better, suspension action. The A-arms ride on bearings and though the LTZ has this design as well, it’s a very cool feature for those who need the most from their suspension with very little stiction. Unlike the Suzuki, however, the narrow yet stable front end provides long-travel suspension without a super-wide stance. Obviously this is a positive for trailies, but a bit of a bugger on the track. The swingarm is also cast from aluminum in a design that Kawasaki feels offers the best blend of rigidity and flex.

The narrow yet stable front end provides long-travel suspension without a super-wide stance.
Even though it’s based off the carbureted KX450F motor, Kawi engineers equipped the 450R with fuel injection to ensure smooth fuel consumption all day, every day no matter the conditions.

The interesting design choices continue in the motor, though some are not quite as effective as they could be. Based loosely on the motor from the championship-winning KX450F dirt bike, the mill in the KFX has been tweaked extensively to deal with the rigors of life in an ATV. The most obvious change is the addition of Electronic Fuel Injection (EFI), but there are many smaller modifications as well. The cylinder is canted a few degrees forward of vertical to fit the chassis better and lower the center of gravity, while the piston wrist pin has been enlarged and the piston itself triple-ringed to deal with the greater effort it takes to spin a quad’s high-grip tires. The intake tract is a sweet system with a rigid polyethylene intake tube negating the need for an aftermarket aluminum airbox (by providing a flex-free, consistent tract size), as well as a coated intake port that offers maximum flow without the need for polishing. Like the KX-F, the KFX features four titanium valves and double-overhead cams, but adds a titanium header to reduce weight even further. The questionable move is the power curve which dishes out the ponies to the midrange, spreading the torque over a wide range of engine speeds to get it to hook-up, but this sacrifices top-end power as a result (more on this later).

The EFI incorporates a 42mm throttle body and a 32-bit processor, which sounds neat, but what does it mean to you? It means no more jetting changes and near-perfect fueling across the board. Kawasaki designed the system for trouble-free performance, working equally well at any altitude, not requiring re-tuning after adding a pipe, and adding instant acceleration when landing big jumps. Riders (especially owners of early YFZs) will truly appreciate the lighter throttle effort at the thumb made possible with EFI as well. Electric starting is a nice touch for non-racers, and coupled with the EFI system actually makes for quick and consistent starting during dead-engine start scenarios like in the GNCC series.

The transmission of the KFX is a slick-shifting beast, with well-proportioned ratios through all the gears, but the real news for off-roaders and cross-country racers is the inclusion of reverse. Kawasaki really punches up the competition merits of the spare gear: extraction from first turn crunch-ups, a chance to back-up and changes lines in a crowded cross-country bottleneck etc, but the real winners here are the average users; regular weekend riders who will be able to engage the stone-simple mechanism and back up under power. Heading out of a trailer, out of a rut or back away from a sudden drop-off, a reverse gear is a sensible thing to have on a four-wheeled vehicle. Kawasaki also declares that with the use of aluminum, titanium and other lightweight materials in other parts of the vehicle negates the weight penalty from conveniences like reverse and an electric starter.

The KFX s front end does a good job of handling abuse from jumps or stumps  but we did notice some deflection and vibration stransmitted to the rider.
The KFX’s front end does a good job of handling abuse from jumps or stumps, but we did notice some deflection and vibration stransmitted to the rider.

Other nice touches include reinforced rear wheels, which Kawasaki pioneered on the KFX700, aggressive tires, a Renthal bar, gripper seat cover, and removable fenders and headlights. Racers and duners will like the modular lights and fenders. Many have become accustomed to using a hacksaw to strip down other quads, but the KFX’s appearance is easily modified without any sort of mutilation and can be pieced together just as easily.

We got the chance to live with the KFX, riding the forests of Oregon followed by some motocross action in Southern California. In the woods and on the trails, the torquey KFX is in its element, confidently tackling a mix of high speed rough and rocky stuff as well as more technical, precision oriented romps through the trees. The suspension provides a relatively plush, controlled ride, soaking-up the terrain, yet feeling very connected to the ground. Our only complaint was that the handlebars fed back too much from trail irregularities, occasionally tossing the quad off of its line or feeling twitchy as speeds increased. Other than a slightly hard seat, comfort was up to all day rides with a well-placed bar and decent peg placement. The gearing is a little tall for super-tight stuff, but no worse than Honda’s 450, and easily dealt with given that the machine has electric start to get it going again, and reverse to back out of a wrong turn, just like a trail machine should.

On the track, it didn’t quite live up to its “race ready” billing as well as we had hoped. While handling and steering was tight and the front shocks did their jobs well, it would still be best to widen this rig front and rear for optimal stability in corners. The slight twitchiness found off-road was amplified in the faster sections of track, wearing on a rider during a long moto. While adjustable aftermarket A-arms or a steering damper should calm it down, it was a bit annoying and will be fairly expensive to tune out. The engine is also not perfectly suited to life on the track. Relatively mellow power down low makes it sluggish at times, and it doesn’t have the top-end squirt needed out of corners to bump it over the next big jump in quite the same effortless manner as some of the other 450s. It requires diligent gear selection and throttle control to successfully navigate the big hits on a consistent basis. Fortunately, the KFX is plenty capable in those categories, but in terms of sheer power help can, and will, be found in the aftermarket with exhaust and final gearing changes. Only time will tell what the motor is ultimately capable of, but the amount of potential as a GNCC racer, MXer or dune-hopper makes it a great multi-purpose quad.

We had no qualms with taking it to the sand for some serious play time.
Features like a reverse gear add to the KFX’s do-all appeal. We had no qualms with taking it to the sand for some serious play time.

The KFX does have a number of features in place to make it easier to hit the local MX scene like those Renthals, top-shelf, industry-first reinforced rims and the stout aluminum frame all held up to our abuse. The tires, which are more of an off-road design that worked well in the woods, didn’t offer the level of traction we needed for the hard Antelope Valley MX Park track surface. Fortunately, the narrow midsection made it easy to hang off and position yourself for maximum traction at all times, something you can’t really change on most quads. As for durability, we didn’t experience any problems, but it’ll take a full season to really see what kind of issues folks start to have with it, if any at all.

In the end, Kawasaki’s first entry into the rarefied air of true high-performance ATVs is a well-rounded effort, delivering excitement on the trail, and capable performance at the track. With the wonderful diversity of approach found in today’s sport quads, you can pick the machine best suited to your needs and not be disappointed. The KFX has features unique, useful, and in some cases not often found on other 450s. Performance is in the ballpark for the market so if reverse and some high-end running gear holds sway, the KFX450R might be your next sport quad.

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