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.
The clutch pull isn’t the lightest, but it does get the job done when stretching those tight corners into a third-gear job. And it has good, biting engagement. At the majority of tracks we tested on, the bike worked mostly in third and fourth, prompting us to try a 51-tooth rear sprocket, which it pulled easily. We think on faster tracks a 50-tooth isn’t out of the question. As when riding most four-speeds, have sprockets handy. Shifting was solid the whole time we were on the bike, from full-throttle upshifts to bringing it down into the turns. And the compression braking on a single downshift wasn’t an issue, just some good trail braking, but double downshifts before slowing are a little harsh.The bike has a slightly tall feel the first moments you are on it. Riders were split between whether the bike felt long or short, but it is way more along the lines of the four Japanese brands than in the past. The riding position is flatter than it was previously, both leading up onto the tank and getting back on the rear of the bike, making it easy to move around on. The tank, sidepanels and shrouds are never too wide and grip well, especially standing. The chassis seemed to fit most riders, but we had taller guys who thought it was plenty roomy and some shorter riders who felt a little cramped. The distance from the footpeg to the seat top is approximately 11/42 inch shorter than on most bikes, which could account for those with longer legs feeling the pinch. There is always the option of moving the handlebar forward, as ours was in the second position for the duration of the test.Suspensionwise, the KTM also makes headway, first in plushness, especially once the fork breaks in, then in bottoming resistance, especially in the rear compared with older SXs. Now using a lighter spring and more valving control, the shock might not span the wide range of rider weights it used to, but once dialed, it gets the job done. For our riders ranging between 160 and 185 pounds, we set the bike-only sag at 35mm (which translated to 107-115mm with rider) and were pretty pleased. We ended up going a couple of clicks stiffer on low-speed compression and added one-eighth and one-sixteenth turn of high-speed compression. This actually held the bike higher and made the shock plusher in the initial travel. A stiffer 6.9kg/mm spring makes a positive improvement for riders above 185 pounds, keeping the shock from packing in the midstroke. Ditto for the front, go stiffer, in most cases two to six clicks depending on the track. The bike really responds to fork tuning, and it is real easy to dial it in, particularly the character of the ride in the turns. On hard-packed turns, tightening (slowing) the fork rebound damping held the bike better in turns.Stability hardly came up, even on fast, rough straights where older KTMs seemed to put a lot more weight on the front wheel, making them a lot more prone to shaking. And as for any kicking on bumps, largely a setup issue on older shocks, trying to minimize bottoming didn’t bother us one bit. For sure, the range of progression on the shock is boosted. We could bottom the fork, it was never serious; a higher oil level or additional nitrogen pressure in the fork bladder should boost resistance. The bike flicks around in the air way easier than before, and the steering effort is just as light as it used to be, one of the reasons riders got the impression that the KTM felt so light.So what’s wrong with the bike? Well, we’re sure putting three-digit numbers on the bike will be fun and scoring them even harder-good thing electronic transponders are all the rage. There isn’t a choice place to grab the bike to throw it on a stand. The nonpipe side provides a good spot, but that puts you, and your fine pants, up against a hot muffler-bad. Stalling was a bit more common on this bike than in the past; it feels like the flywheel is a little on the light side. It isn’t the problem it would be if we had to kickstart the SX-F, but stalling is stalling nonetheless. The brakes are the strongest you’ll find on a production bike, and even after you get used to them, they can be too strong. Either that or they are just the best brakes on the market and we aren’t good enough riders to use them properly, but nevertheless, every rider noticed the strong brakes. We got the rear tire to rub on the muffler, and the front tire grinds on the fender when it bottoms and flexes, also touching the exhaust header on severe nose landings. The chain needed adjusting every three motos, and it is still stretching. We’ll bet taking out a link or two could really tighten up the handling with a slightly shorter wheelbase. On our last day on the bike, 215-pounder Steahly bottomed the bike hard enough to pop the front tube. And on the next ride, Lewis blew up the rear wheel, breaking (stretching apart) more than five spokes. KTM had experienced spoke issues a few years ago, and it is looking into its spoke manufacturer now.As always, we’re baiting the hook for the upcoming shootout to see where this bike really stands, because that is truly the only way to tell. But we can definitely say that this is the best KTM motocross bike we’ve ridden to date, and it can only get better as KTM further refines the new chassis, suspension and engine. Lots of little things in the settings, especially in regard to the suspension, could make this bike even better. Every test rider was impressed after riding the bike, and that is a first in our dealings with KTM motocross bikes.
I never thought the KTM 450 could come so far in such little time. It has excellent handling, astonishing brakes, good suspension and it looks like a pro factory MX bike. It didn’t take that much time to adapt to because it is very friendly. The engine felt strong and tamed; I was never losing control. The bottom-end torque was great on the bike because it allowed me to hit corners in third gear, providing good momentum; there is power available whenever you need it. The Brembo brakes need some time to adjust to, but when you get them down, you will enjoy the strength, which allows you to go very deep into the turns and tight corners. The KTM 450 also feels much lighter than the CRF450R, which provides the bike with excellent maneuverability on jumps and on all obstacles. The negative parts of the KTM 450 are that there is no place to grab the bike when you want to lift its tail up on a stand and the front tire hit the fender while the rear tire hit the muffler.-Juan Diego Saffon/5’10″/160 lb/ProBefore even getting on the bike, the first thing I noticed was the electric start. With four-strokes being difficult to start at times, this is a major plus. Once I got on the bike, I noticed the footpegs felt a lot higher than on my Honda, or it’s possible the seat sat lower on the frame. For sure, after riding CRFs for four years, the KTM took a little getting used to. On my first moto, it seemed as if the suspension was too stiff-it felt as if every little bump I hit or jump I slightly overjumped sent me bouncing. Then we played with the suspension, and the bike was completely different. It absorbed braking and accelerating bumps like a Honda! Just from being a few clicks stiffer! It also took a while to get used to the four-speed transmission. The brakes were never consistent; they were either off or locked up. It seemed as if it was harder to time the speed of hitting a jump, especially when I had to rev it out. One trait I really liked was if I pointed the bike into a rut, it would get me there and stick in-its cornering is unbelievable.-Chris Dvoracek/5’11″/165 lb/IntermediateWhen I saw the new KTM 450, I was impressed. The bike has an awesome look to it, inspired by the Dakar Rally bikes. When you sit on the bike, it feels really comfortable. The riding position felt perfect to me. The seat is the most comfortable of all the MX bikes I’ve ridden, and the bar fell into place. The gas cap is much better than the small caps that KTM used to make. Also, the electric start is awesome. I don’t care how much weight it puts on-it’s worth it. I just think that kickstarting the 450s is a hassle. Everyone will love the electric start. After riding the KTM, I thought it felt longer than the past model. This is good because the bike felt really stable at high speeds. The suspension was also improved. The bike feels a bit unbalanced. I think the shock felt better than the fork. The KTM turns steadily on the fast flat turns, but it stood up on the tight, rutted turns. I’d also overshoot some lines in turns because the bike wouldn’t let me go into the line I wanted. Sometimes jumping it was the same. If you tried to move the bike around, it was a bit hard. The motor was really strong, with smooth power everywhere. The exhaust also kept the bike quiet, which is good. On a fast straight, the KTM needs fifth gear. It just didn’t feel good going wide-open in fourth gear, as the engine is too aggressive. Overall, I think this is the best KTM ever, and it has an awesome look. Taking into consideration all the things KTM offers you (components, electric start, etc.), this would be the bike I’d buy.-Alfredo Contreras Macklis/5’9″/175 lb/IntermediateMy biggest problems on the MX track with 450s are being intimidated by the power and worrying about overjumping landings, which makes me unable to really get comfortable on them. I felt at ease right away on the new KTM. The power is very easy to manage, with no crazy hit. Jumping the bike was easy; it felt light and nimble in the air. On the ground, it was the same, with a more predictable and precise manner than previous KTMs. The shock was a little harsh on acceleration chop because of my weight; it forced me to stand up more than I wanted to, but going up to the 6.9 spring worked wonders for the suspension, front and rear. I don’t know whether I love the new look and KTM should get two thumbs-up or if it’s the ugliest thing on the track. But I’m sure it will grow on me.-Derek Steahly/6’1″/215 lb/Novice MXSpecifications
Claimed dry weight: 229 lb
Actual weight (ready to ride, no gas): 233 lb
Seat height: 37.7 in.
Seat-to-peg distance: 17.0 in.