By definition, a pioneer breaks new ground and leads the way. KTM fits that description, not by playing with crazy innovation that borders on the weird science stuff, but by modernizing and refining its engineering concepts; the company has never been scared of tapping into a fringe market or breaking rules in the process. This 450 SX-F is just the next logical step for KTM and its plan for conquering the most competitive class in motocross.One look and you can see this SX-F began on a clean sheet of paper. Everything is fresh from the ground up and designed strictly for MX, as KTM sees it. The biggest news is the absence of a kickstarter, as it has only electric starting. KTM is hedging its bets with the inclusion of two batteries, a 3 and a spare 4 amp/hour battery, the larger, 1-pound heavier battery for those cold mornings when you might need some extra cranking juice. Following that is a completely new engine. KTM has been running the top end on the old lower end on selected race bikes for some time to get it tuned and flowing the way the company saw fit. Sitting on top of the new cases, it is one of the most compact engines, looking more a 250F than a 450.Inside the major aluminum castings, the engine is designed to be very rigid for high-rpm running, especially the head. Everything from the dual counterbalancers to the cam drive system is built to be stable and to multitask as much as possible. For instance, their drive gears not only double as counterbalancers, one on each side of the motor, but also act as the coolant impeller gear and drive the cam chain. From there, the cam chain leads to another intermediate gear, like on the KTM 950 motor, which in turn spins the cams, making for a shorter and straighter cam chain. This valve-train setup means maintenance is easier and there is less variance than with a chain-only, especially at crazy, rev-limiter rpm. Two oil pumps suck from a sump below the crank. Oil is channeled internally to the cams, crank and spilled off into the transmission. A single filter and a screen provide debris protection. Now there is quick access to the clutch and all the darker-colored covers are made from magnesium. The transmission is using a new gear changing and shift fork system about which KTM isn't making much noise, and we'll have to see it apart to grasp it, but it must be compact.The chassis design is centered on a chrome-moly frame. It uses a traditional centered backbone and goes to oversize oval lateral tubes that are more angled. The lower tubes are hexagonal, not round. The cast-aluminum swingarm is tuned for the linkageless PDS shock and has some of the stoutest chain guide hangers we've ever seen. Now the WP PDS shock is laid down further, has a more progressive curve and, since it is longer, has more control of the stroke with valving. The spring is also significantly lighter in rate, now a 6.6kg/mm down from the old 8.6kg/mm. Up front, the new fork hides a lot inside. It has nitrogen-filled bladders and a smaller 12mm cartridge tube, working more like a shock damping system inside of the fork leg. Shorter and lighter springs are used, and they are attached by the super-adjustable KTM triple clamp with two offset positions, 18 and 20mm, plus four handlebar positions.The plastic will draw instant attention, and we're sure the AMA is going to have a fit with the sidepanels (or lack of them). First, the riding position is engineered around having the fuel as low and, more important, centered as possible. And thinness wasn't the first priority, either; fit was, giving the rider something to hang onto with his or her knees when sitting and standing. The seat has a very flat layout, and though higher in the middle, it is lower in the rear of the bike. The footpegs are a bit higher than on other bikes, but overall, especially at the footpegs, the bike feels thin. The brake pedal is no longer hard to find, and the seemingly high placement of the bar in reality gives a roomy feel.You'll never complain about electric starting, as long as it works. And we damaged our lighter battery somehow (most likely a cracked cell, as it held a charge but without any cranking power), and it did fail after a couple of track days. So we hooked up the heavier battery supplied with the bike and never looked back. The biggest problem with the electric starting was the number of test riders who burned their gloves reaching for the nonexistent kickstarter. Out in the woods, it is good to have a backup, but at the MX track, it's not a real issue-that missing kickstarter was longed for the way a flat tire would be.Once running, the new RF4 engine has a snap and crispness to it that make the old SOHC RFS motor seem, well, enduro. Just like the 250 SX-F but one step further. There is a little mechanical whine-blame the spinning gears. The 41mm Keihin carb was jetted spot-on for warm temperatures and for altitudes up to 4000 feet. Yet with all this talk of the improved power, KTM didn't forget to make the motor smooth. Even when boasting extremely high peak-horsepower numbers (which we believe), it feels like the numbers on the bottom are in line, if not a little less than some of the other bikes. The bottom and midrange are linear and progressive, with plenty of torque to pull a gear high or lug around the track. You can ride in the low rpm range and use big throttle openings without the consequence of bog or the bike ripping out of your hands. Run it up onto the top and the bike really begins to come alive, as there is such a big surge and pull that hitting the rev-limiter is pretty rare. In fact, we found the biggest shortcoming of the four-speed gearbox was rough high-speed straights when you were pinned. The bike wanted to lift the front wheel when you'd have shifted and run at a lower rpm (and less power) on a five-speed bike. Inside the ignition box, there is a second curve-less aggressive on the top-end, activated by disconnecting a wire or through a KTM Hard Parts switch. We tried it and didn't notice much difference. There isn't a problem pulling the gaps as the gear ratios are typically what second through fifth would be, just geared lower in the final drive to shift down the ratios. A couple things are for sure: This bike revs, is willing to rev and makes boatloads of power up top for the rider twisting the throttle. It will surely be an easy transition for a 250F rider.