The days of converting your big-bore four-stroke motocrosser into a true off-road machine are waning. Why? With companies like KTM, Beta and Husqvarna building truly superb and dedicated off-roaders, it’s not really necessary. But our buddy, Dick Wilk, has been building high-performance racing machines for 35 years, and he likes a challenge. He believes that the Kawasaki KX450F is the best platform for a conversion because of its good suspension, easy starting (for a non-button bike) and broad power. Dick worked with longtime friend and former national motocross champion Chuck Sun and a bevy of companies to make the off-road concept into a reality.
In Dick’s words, “The stock suspension is pretty darn good—on a moto track. Off-road, it deflects off of rocks and ramps up too quickly to absorb the majority of terrain. This can be said about all MX suspension; it is not designed for the off-road environment. My goal with the KYB air fork was versatility. I wanted a setup that was plusher for off-road yet still capable of doing motocross. To achieve this, the fork was modified using a special mid valve that took the spike out, making the action much smoother. In addition, the high-speed compression valving was reduced to lessen the ramp-up effect. Combine this with rebound damping that lets the wheel follow the ground without packing and you have a front end that floats over everything in its path. Special oil at a lower level was used to improve seal life and free up the end of the travel without bottoming. We used 34 psi off-road and 36 for MX, and we used Works Connection rotating air valves and an air pump.” As for the shock action, Dick said, “Out back, the shock was fitted with a stiffer KYB 5.7 spring for those of us tipping the scales at over 200 pounds. Setting the correct preload is next to impossible without the use of an X-trig adjuster that works by just turning an 8mm screw. This one little mod makes rear spring setup almost criminally easy. Internally, the compression valving was altered for smoother action and the ability to absorb square edges, which it doesn’t like to do in stock form. The rebound valving was matched to the stiffer spring, allowing the rear wheel to hook up better over hacky terrain and acceleration bumps coming out of corners. A special bleed port is machined into the shock body to ensure that no air gets trapped inside during assembly, which is absolutely critical for proper function. Once the shock is air-free and assembled, a high-volume bladder cap is installed to assist in filling the shock with nitrogen.”
It’s no secret that the KX has an incredibly versatile and strong 450 engine, which is why so many people ride and race it. Making it better was no easy task. Dick’s Racing has developed an engine package that manages to make more power that is smoother and easier to control. It involves a No-Toil Super Flow air-filter screen-eliminator kit, an FMF 4.1 muffler with removable spark arrestor, and an R&D Genius throttle body. Dick pointed out that the throttle body is a huge investment and not for everyone. But once it was setup, he loved the performance gains. According the Dick, “All current throttle bodies have two inherent problems: turbulence and proper air control. Both of these problems are created by the butterfly valve mounted vertically in the body, which has the air running into a wall, causing turbulence. Then it’s allowed to enter the engine from both the top and bottom as the valve opens, which causes jerkiness initially and an unwanted pressure drop afterwards.” Dean Dickinson is the mastermind behind the Genius throttle body and has worked closely with Dick’s Racing to solve these issues. The design of the new CNC-machined body is the key, incorporating a round, cylinder-shaped valve that has a half-round cutaway that opens from the top down. This design precisely meters air, letting it enter at the top, where the injector is, so the air/fuel can atomize efficiently. The round shape of the valve also reduces the disruptive effects of turbulence. Modern fuel injection works great, except for the lack of tuneability. When you start changing things like pipes, mufflers, air filters or anything that affects engine performance, proper air/fuel ratios are compromised and performance suffers. With carburetors, you could change jets based on symptoms and seat-of-the-pants experience. Those days are gone. Now, the only way to accurately alter fuel delivery is to put the bike on a dyno and measure those ratios at every rpm and throttle opening via a sensor installed in the header pipe. To make changes that requires a special computer software mated with an ECU that controls the injector that is capable of being altered. For this project, a Vortex programmable ECU was used, allowing perfect fuel ratios to be installed across the entire powerband. It can store 10 different maps, and in this case that means a base map for an open muffler +2 richer and 2 leaner, then a base map for the spark arrestor with +2 richer and leaner maps. The maps can be easily changed by turning a screw behind the front number plate. The unit also has three separate dials (low/mid/top) for making bigger changes in addition to the base maps. It is complicated and time-consuming as well. Luckily, it is a simple bolt-on that requires no tuning as long as you are using the complete package, meaning the same pipe, air filter, throttle body and ECU. For tight off-road work, Dick’s went with the Rekluse Core EXP clutch. This is the auto/manual unit that reacts likes an automatic (no clutch necessary) or with the clutch (feathering just like a normal unit) it lets you control the power. The original goal was to make the hard-hitting KX450F more tractable and less prone to stalls in tight terrain.
–The big KX hauls the mail, but eventually you have to stop. The stock front brake is weak compared to a KTM’s, so an EBC oversized front disc kit was used to improve stopping power. –The stock chain and guide wear out quickly and were replaced with a Renthal O-ring chain and TM Designs Slide and Glide kit. –The KX450F is stable and doesn’t shake at speed. Still, we used a Fastway steering damper that featured separate high-/low-speed adjusters to make it easier to hold on when hitting trail junk. Big bar clamps with an adjustable damper mount allowed us to use the forward-bar mounting position for taller riders. –Works Connection provided blue rotating bar clamps/brake caps and a clutch perch assembly/brake lever for a smoother pull than stock. –A Renthal Fatbar was used with AME bolt-on grips. –Attack Graphics made the custom plastic coverings that fit perfectly and look great. –The IMS oversize fuel tank was easy to install and extends fuel range. –The Hammerhead shift lever is way tougher than stock and has optional different-length tips. –Dunlop AT 81 tires were used for their all-around performance. –Works Connection makes the best aluminum full-coverage skid plates. We used Works Connection’s rear-brake master cylinder guard and radiator braces as well. –Dick’s Racing only uses Fastway handguards because of the unique mounting point that allows them to move with bar flex. Dick’s uses STR threaded bar inserts for handguard applications.
MOSEYING INTO THE WOODS
There is no doubt that the KX450F is a weapon designed for fast, hard and nasty terrain, not quick, tight and ugly. On our off-road loop, the machine shined in the more western-like terrain, whoops and faster zones. Dick’s suspension mods were stiff yet plush. Traction was improved, and the ability to push it hard was enhanced with newfound stability and control. Power-wise, the sucker was super strong, very broad and, for a 450 motocrosser, totally rideable. It almost never flamed out, made power right off idle, and felt smoother, stronger and broader than stock. There were no hitches or glitches during acceleration, just major amounts of juice. In the fast stuff, we barely noticed the Rekluse Core EXP clutch. Once we segued into the tight junk, rocky canyons and vertical gorges, the auto feature blossomed. It would chug and torque where the stocker would belch and vomit. Still, this is a lot of bike in the tight stuff and really requires the right dude behind the wheel. Our final thoughts? If tight were our priority, we’d find something easier to ride with a more versatile transmission and ratios that cater to the tight factor. The KX is geared tall, with a big spread from first to second, and forces you to stay in the power and push it rather than shift up and baby the throttle. But if fast and fun, fast and hacky, or hill-climbing and whoops are your forte, then it doesn’t get a whole lot better than the Dick’s Racing KX450F. Honestly, the Genius throttle body is a tough pill to swallow. It’s overkill, but man does it make for big gains, smooth power and glitch-free throttle response! As for the rest of the package, plushness, durability and off-road control were the goals, and Richard succeeded quite nicely with the project KX450F. Dick’s Racing can modify your suspension and carries everything in stock to make your off-road conversion easy. Check out www.dicks racing.com or give them a call at (916) 705-3193