All-Wheel Drive Motocross
When I tested the Christini AWD Honda CRF250X two years ago in the rugged mountains of Pennsylvania, it was nothing short of a complete revelation. The Christini mechanical all-wheel-drive system upped my off-road game to a level I never thought possible, taking me on trails that I consider to be absolutely impassible and unconquerable on a standard rear-wheel-drive motorcycle. I was stunned.
As a quick rundown, the front wheel is driven at 80% of the speed of the rear wheel. In high-traction conditions, the rear wheel drives faster than the front and one-way clutches within the front hub allow the front wheel to passively freewheel. Though the front portion of the AWD system is turning, it is not transferring power to the front wheel. When the rear wheel loses traction, the drive ratio, relative to the bike’s forward speed, changes. The AWD system engages, delivering power to the front wheel until traction is reestablished at the rear wheel and the freewheeling returns to the front. While this may sound complicated, the all-mechanical system is actually quite simple and acts in a purely transparent manner.
Kawasaki decided to take its own look at the Christini AWD system, and had it installed in the KX450F motocrosser as an in-house project. The KLX450R off-road bike would have seemed like a natural choice, however the location of the electric starter and countershaft sprocket make the conversion impractical.
In addition to the Christini kit (modified frame, modified forks, custom fuel tank, custom Talon AWD hub, complete AWD System with engagement switch, CNC triple clamps
, and fork guards), the KX450F had the optional KX FI Calibration Kit, a Yoshimura Pro Series RS-2 Full System titanium exhaust, Hinson Racing clutch components (clutch cover, clutch basket and inner hub and pressure plate kit). Also, the Christini fuel tank was replaced with a custom carbon fiber unit.
Off-road, with the KX’s close-ratio transmission and supercross-ready power delivery (thanks to the Yoshimura pipe), the bike can be a handful. As all of the power is delivered to the ground, corners arrive extraordinarily quickly in single-track conditions. Loose hillclimbs are still magic. We tried switching off the system for a particularly nasty climb. We repeatedly stalled the bike, trying to work our way to the top, throwing loose rocks in all directions in a futile effort by the 19-inch Bridgestone M404 to find traction. The Hinson clutch was abused, but refused to slip over overheat.
When the KX450F was switched back to AWD, the bike easily and controllably topped the hill, making the rider wonder if an entirely different bike has been substituted. Quite simply, the difference in these sorts of situations (mudholes are another), the difference cannot be overstated. It’s the difference between painless success and unqualified failure.
In any sort of loose terrain, the difference is staggering. Sandy uphill turns that can flummox a rider become a minor effort as the front wheel pulls the bike/rider combo up and through the turn. Even when installed on a motocrosser such as the Kawasaki KX450F, the Christini system retains its indispensability off-road.
On the motocross track, our opinions were mixed. Starts are certainly an advantage, as the rider simply leans forward and lets the KX450F rip. With the front end pulling, there’s no wheel spin or wheelying. It’s pure acceleration to the first turn-a definite advantage.
Cornering was a bit trickier, with one test rider launching himself over a berm when the KX450F’s front end hooked up unexpectedly, giving him more velocity in an unintended direction. However, once the importance of pointing the front wheel where you want to go was ingrained, and the knowledge that the bike was not going to slide in a bermed turn, the cornering was predictable and effective.
I had an interesting cornering experience on a private motocross track. The turn was an uphill right-hander, slightly off-camber on a hardpack track with pea-gravel on top. This is a tricky corner! In my case, the KX’s back end drifted fairly far to the left, but as the rear wheel was spinning and not putting much power to the ground, the front wheel was pulling me up the face of the turn. It was an unusual experience, but quite liberating. In RWD only, the back end slid out and forward progress virtually ceased. Christini’s AWD is amazing in conditions such as this.
The Achilles’ Heels on the MX track is its oddness when jumped. With a powered front wheel (any application of power in the air transfers power to the front wheel, of course), the attitude of the bike is a bit more difficult to control. And, when landing, care has to be taken due to the Bridgestone M403-shod front wheel turning on its own. More time on the bike would certainly have helped us develop a more useful technique on a motocross track. Its our feeling that the Christini AWD system is not ideal for jump-infested supercross tracks, but certainly is viable on vet-style natural terrain motocross courses where airtime is limited.
The KX450F ran perfectly. We were instantly sold on the EFI system for off-road riding. Though it lacked the convenience of an electric starter, the EFI makes for almost effortless kickstarting. Like my Honda-powered Montesa Cota 4RT (also EFI-equipped), all it takes is an easy push (not kick) through the kickstarter arc to get things fired. I was able to easily start the KX450F when it was cold and I was in sneakers, on the first kick! So, the magic on this bike is not restricted to the Christini AWD kit. The Kawasaki KX450F is a formidable motorcycle on its own.
Photography by Don Williams
Helmet: Shift Agent
Goggles: Utopia Slayer
Pants, jersey and gloves: Shift Faction
Chest protector: Shift Proflex
Boots: Alpinestars Tech 10