Over the years the Kawasaki KX450F has developed a reputation for not only being one of the most race ready motocross bikes out of the crate but also the MX bike of choice for plus-sized riders. Its robust engine performance, stiffer suspension settings and well proportioned cockpit have made it a very competent motorcycle to ride in a skilled person’s hands. However, a significant portion of riders still prefer to ride on trails off-road as opposed to jump-laden motocross tracks. That’s where Dubach Racing Development comes in. They modified Team Green’s 450 to make it more accommodating for off-road riders in their chosen field of operation.
Hop onto the seat and the DRD KX450F still feels sizeable but not drastically different from the 250-pound stocker either, which is a surprise considering some of the added componentry including the
IMS Large Capacity Fuel Tank (0.8 gallons bigger than stock). The seat actually feels a little lower as compared to the 38-inch high stocker which can be attributed to the lighter suspension spring rate in the fork fitted by the dirt bike suspension tuning gurus at Factory Connection (more on that later).
Grab the
ProTaper EVO Handlebar (Carmichael bend) and you’ll feel that the position is lower and has more rearward sweep compared to the stock Renthal. We’re not super picky about our handlebar bend so they worked fine for us and should be appreciated by riders of average height or those who prefer a lower bar. Although we couldn’t really feel the difference we like the look of the gargantuan ProTaper footpegs and their three-way height adjustment. Further cockpit upgrades include the soft feel of the black ODI Half-Waffle grips, ARC Axis clutch perch, front brake lever and hand guards.
A feature that we absolutely love about Kawi’s fuel-injected 450 is just how easy the engine is to start regardless if the engine is hot or cold. So it’s no surprise that this DRD KX fired right up on the first or second kick.
Hammer down on the right grip and it’s immediately apparent how much more refined the powerband of the engine feels. Bottom-end power is softer and ramps up far more smoothly allowing the rear knob to hook up with reduced wheel spin. Keep the throttle buried and the engine spools in a muted fashion, not surging through the rev range like its motocross brethren. Instead it feels almost like a turbo-diesel truck, pulling the rider forward with a very high level of torque feel. While it might not be optimal for a quick 20-minute moto, during an hour-long GP or off-road race we could see how it would prevent rider fatigue. The substantial change in the feel of the powerband can be attributed to the fitment of a Simon Smart Body (SSB) throttle body.
The SSB functions like a mechanical carburetor. It actually features a smaller bore (38.5 vs. 43mm) and meters intake charge via a vertical slide opposed to a butterfly valve. SSB claims that this improves the intake speed of the fuel. It is also said to increase the efficiency of the engine and reduce fuel consumption.
On the exhaust side DRD fitted its top-of-the-line
Dr. D Titanium Exhaust System. As opposed to other pipes this one features a spring-less design in which header, mid-pipe and muffler simply plug into each other. Another interesting design note is the employment of metric fasteners instead of rivets on the muffler body which allow the user to easily service it or to remove the USFS Approved Spark Arrestor. DRD’s pipe sounded on par with a freshly packed stocker and top-end engine performance felt strong and didn’t fall off at redline.
In spite of it carrying a few extra pounds, set the DRD-modified KX450F into a corner and you’ll be surprised by its low-speed agility. While it does take a little more effort than most other 450 MX’ers, it steers in and out of corners predictably. Part of the reason can be attributed to its lower center of gravity courtesy of the
DR. D Radiator Lowering Kit. The kit consists of machined aluminum brackets that physically lower the mounting position of both radiators. A bike that steers so easily might be assumed unstable at speed but the chassis remains composed and feels almost truck-like in its ability to just blast across obstacles with minimal head shake.
(Above) We were surprised at just how agile the KX450F was in slow speed corners. (Below) DRD-modified 2010 Kawasaki KX450F had friendly engine power that was easy to manage.
Aside from proper chassis geometry, credit goes to the suspension tuning wizards at
Factory Connection. Inside the fork FC installed lighter fork springs (0.46 versus 0.47 kg/mm stock) as well as lighter pressure springs. For the shock they retained the standard 5.5 kg/mm shock spring. The valving shim stack was modified based on FC’s grand prix-spec. Initial compression damping was softened both fore and aft which in conjecture with the fork spring change will offer suppler feel over small bumps and allow the components to settle into the stroke with added control. As the suspension slides deeper into its stroke the damping capabilities ramp up progressively. Bottoming resistance was also beefied up. Furthermore the shock received FC’s Compression Piston Plate and High-Speed Compression Spring which is designed to be more reactive at high shock speeds as encountered over square edge holes in the terrain. The fork was re-filled with its in-house 5wt fork oil while the shock was topped off with 2.5wt oil and then re-charged with nitrogen.
Despite having accumulated a fair amount of riding time on various Kayaba suspension equipped KX450Fs, this Factory Connection GP set-up felt nothing like anything else we’ve ever experienced. Most notable is how much more plush of a ride it delivers. While it lacked a bit of outright damping during heavy braking or when loaded on larger, more high-speed obstacles in slow-to-medium speeds we’ve never experienced a KX that floated across earth this well. This works in unison with the tractor-like pull of the engine, which allows riders to make almost ridiculously rough line choices that they’d be hesitant to take on a stock dirt bike.
Since the DRD-modified KX450F gained a few pounds in its off-road conversion the braking capabilities would also need a boost. So DRD fitted a QTM oversized front brake rotor kit. The kit consists of a larger diameter disc, caliper re-location bracket and a matching set of pads, though AP Racing pads were fitted in our test bike. Both the front and rear brake were then augmented with steel-braided brake lines. Despite the added heft this KX actually felt like it stopped better than a stocker. Even better was the enhanced level of brake feel which made it easier to extort maximum braking force when needed.
Riding and racing off-road can be very hard on equipment so if you want your machine to last it’s a good idea to make a few upgrades for the sake of durability and peace of mind. One of the most valuable accessories that we religiously invest in is a quality hour-meter to track engine time. DRD agrees, so it mounted up one of its affordable
DR. D Hour Meter. Other durability enhancements include the tough TM Design Works Chain Slider, MSR chain and CV4 radiator hoses. Bling is also another factor when customizing a dirt bike so LightSpeed carbon fiber fork guards, skid plate and frame guards were fitted along with a Decal Works DRD Graphic kit and an anodized Hinson clutch cover.
The smoother powerband makes the KX450F less fatiguing to ride.
Having only logged motocross time aboard Kawi’s KX450F we were surprised by just how adept the bike is with an off-road set-up with a few minor modifications. The Simon Smart Body really expanded the powerband and made it easier and less fatiguing to explore. Factory Connection gave us a taste of how smooth and forgiving an off-road suspension can be. While handling, braking and the layout of the cockpit offer greater rider-tailored performance from companies like DRD, QTM and ProTaper.
