KTM North America has officially announced it’s ready for ATV motocross. New for 2009, the 450 SX and 505 SX race ATVs — which made their debut in May at the Motorcycle Fair in Barcelona, Spain — join their XC brothers in the KTM family.
According to KTM, “everyday is race day,” and these models are purpose-built for ATV motocross and all that it demands. Two areas of concern for any true MX performance quad are the engine and suspension package and KTM says its new SX models are thrilling in both areas.
“Ready-to-race, these motocross sport ATVs feature the most powerful engines and sophisticated suspension elements in the industry,” says KTM.
“Both engines are derived from the 450 SX-F dirt bike mill,” says KTM, “but it has been reconfigured for use in a heavier quad chassis.” KTM engineers redesigned the engine cases with a modified engine ventilation system. The new setup accommodates a deep oil sump allowing improved engine performance and additional oil capacity.
A closer look inside the engine reveals a similar four-valve dual overhead cam design used in the SX bike. Unlike some of its ATV competitors, however, the KTM is carburetor fed. Both quads are fitted with the proven Keihin FCR-MX 41mm flat-slide carb, which is the largest in the class. That’s a 2mm larger venturi than the unit found on the KTM XC models and the Polaris Outlaw 450 MXR, which uses a very similar KTM powerplant.
KTM calls the Keihin carb “ultra responsive and easy to tune.” This carb has been outfitted with an acceleration pump, throttle position sensor (TPS), hot re-start function and a high-capacity float chamber with a baffle for rough terrain.
The larger carb also works better with the SX machines’ 12.5:1 compression ratio, because it produces the best performance and efficiency. Also, that’s the largest compression ratio in the 450 class. Both the Honda 450R and Kawasaki KFX450R use a 12.0:1 ratio.
The tranny is a close ratio five-speed without reverse, which is not needed for MX racing. KTM says the tranny has been configured to provide the right gear for all track conditions. Both quads fire via electric start.
Suspension Along with impressive power, an MX machine must be able to transfer that power to the ground (find traction), do it in the roughest of conditions and keep the rider in complete control. The 2009 SX models wear industry-exclusive fully adjustable WP piggyback shocks. The front and rear shocks are adjustable for high- and low-speed compression, preload, rebound and crossover height. KTM says they come tuned for motocross.
ATV Sport
The shocks are bolted to wider, adjustable chromoly steel dual A-arms. KTM said its engineering team’s goal was the 50-inch MX width gold standard. The A-arm shock mounting location is identical to XC models.
The KTM comes with a highly desirable adjustable rear axle, so riders can alter its width — from 47 inches to 50 inches — depending on race conditions. The rear WP shock connects to a chromoly steel swingarm, which KTM says is lightweight and motocross specific. The SX swingarm has a different rear shock mount location than the XC models.
Other Features KTM modified the SX models to differ from the XC machines specifically for MX racing. Both quads are outfitted with 10mm of raised steering stem height and 14mm reduced seat height. Also, both SX units are California Green Sticker legal.
2.7-gallon fuel tank with on/off switch (no reserve)
Five-speed manual transmission without reverse.
A 1/4-turn quick-release fuel cap.
Lightweight DWT aluminum rims with rolled edge. Rear beadlock and 8-inch wheel.
ATV Sport
Soft-compound, four-ply Maxxis Razr MX tires (21 x 6-10, front/18 x 10-8, rear).
Nerf bars and headlight cover come as standard equipment.
When Will You Ride Them? We expect to ride the new SX models sometime late this summer, and KTM says they will be released around that same time. Pricing was not released as of press time.
2009 XC Upgrades Although they may seem too new to alter, KTM announced it has already tweaked its impressive 525 XC and 450 XC for 2009. KTM says both models took on “several changes,” and highlighted a few of those upgrades in a press release.
Two changes involve the quad’s ergonomics. The first change was the thumb throttle was positioned forward 10 degrees for improved comfort. Both models have a new seat cover for an improved feel and comfort. Also, new plastic bolts, in order to economize aluminum bushings, were added to each XC quad.
