KTM 450 SX-F Factory Edition | Dirt | First Ride

Do It Like Dungey!

By Karel Kramer, Photography by Karel Kramer

They say: “The next-generation 450cc motocrosser.”
We say: “With a supercross pedigree.”

Traditionally, the most successful off-road racing motorcycles have resulted from a factory modifying a cutting-edge motocross bike. It’s more than a little ironic, then, that KTM’s most successful foray into AMA Supercross was reverse-engineered from a street-legal dual-sport bike! KTM pulled out all the stops to develop a mount for new recruit Ryan Dungey, but building a bike for the 2010 champ was only half the problem. The AMA’s production rule meant KTM needed one for Dungey and 399 more to be legal for racing!

The bike to entice Ryan to rejoin his mentor, KTM Race Team Manager Roger DeCoster, needed to be a 450, but the current 450 was carbureted, not fuel-injected. Rather than embrace technology like the 350 SX-F's finger followers, KTM chose simplicity.

Switching from sand-cast to die-cast engine cases saved 4 lbs., and rescued KTM from the ignominy of building a new fuel-injected machine that weighed more than the old carbureted one. At less than 250 lbs. wet, the FE is perhaps the second-lightest bike in its class—and the lightest with electric-start.

Starting with the 450 EXC made sense, because that bike’s engine was designed with reduced rotating mass in mind. Eliminating one cam saved 1.8 lbs., and all other parts were examined and lightened, removed or integrated. The bore and stroke are unchanged, and the lightweight Koenig 12.6:1 piston is a “box-in-box” design.

The EXC’s rocker arms use compact rollers, but the FE uses a V-shaped rocker for the intake that employs a DLC-coated slide instead of a roller. All four valves are titanium with lightweight springs and retainers. The camshaft itself is lighter with new timing, and the combustion chamber shape and head porting are different.

The result is a single-cam engine that gets more power to the ground and accelerates harder than the twin-cam it replaces. Despite being rated at nearly 60 bhp, it feels more docile and controllable at small throttle openings, and doesn’t have a snappy hit in the midrange so much as it leaps ahead keeping the front end light.

The handling is a pleasant walk between desert-racing stable and supercross-quick. Suspension action is plush enough, and bottoming resistance is far better than past efforts. Changes to the frame like a crossbrace in the steering head and a 2mm-larger (25mm) rear axle allow the stiffer suspension settings without undue harshness or loss of traction feel.

KTM brought in a team manager and a rider that can push the package to new levels, and learned from their input. No doubt the FE is the finest KTM motocrosser ever!

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