Long ago, Honda, Yamaha and the other Japanese manufacturers trained us to believe that no street-legal motorcycle could be a competent dirt bike. DOT equipment made them fragile, emission equipment made them run poorly and safety equipment made them heavy. Husky, KTM and Beta changed the game. Since 2007, the European makers have offered bikes that needed only slight modifications to be dirt-worthy. In the face of ever-tightening regulations, though, the job is tougher than ever. Even off-road bikes are faced with difficult emission and noise restrictions. That’s why KTM dropped its trail bikes in 2017. If the company was going through all the expense and effort to make a bike clean and quiet, it made sense to go a step further and make it street-legal. All of KTM’s current offerings that aren’t closed-course, competition bikes are fully street-legal this year. As such, dealers, aftermarket companies, journalists and even private parties aren’t allowed to alter the emission or noise equipment.
So the brand-new 2017 KTM 500EXC has high expectations. It has to carry the torch for both the dual-sport bike it supersedes, as well as the now-discontinued 500XC-W trail bike. The single-overhead-cam motor is loosely based on the one in the 450 motocross bike that was new in 2016. It has a six-speed transmission instead of a five-speed, the stroke is 8.6mm longer for a displacement of 510cc and the cases are different to accommodate a kickstarter. There isn’t a kick-start lever there in stock form, but KTM theorizes that dual-sport guys are more likely to mistrust the electric starter and want to install a manual starter as a back up. It should be noted that if the lithium battery is completely dead, there won’t be enough juice to power the EFI system and it won’t start anyway.
In order to make a street-legal bike out of a motocrosser, KTM engineers had to work hard. In addition to emissions restrictions, the EPA has a drive-by noise test that’s very difficult for an off-road bike to pass. Just having a quiet muffler isn’t enough. The intake, chain and tires are contributing factors. Everything KTM did to make the bike quiet and clean is legit; there are no “fake” measures like a throttle stop or a peashooter in the muffler. After testing and more testing, engineers borrowed technology from the automotive world and installed a reed valve between the air filter and the throttle body. The design, which KTM calls “velocity-focused intake,” killed just enough intake noise so that the airbox could be more open. The company’s in-house test riders also say that the reed actually increased low-end torque. The bike uses Continental TKC80 tires, which are not only DOT approved, but have closely spaced knobs that produce less rolling noise.
Everything about the EFI system is new for 2017, including the Keihin throttle body and EPA-approved fuel mapping. Unlike the motocross bike, the system is said to be fixed; you can’t change to a richer or leaner map with a laptop. We hear that jail-breaking the system is possible, but shops who do this risk big consequences, particularly in California. There are companies that make piggyback EFI tuners that change the mapping by hijacking and altering the signal between the motorcycle’s central processing unit and the injectors. These, of course, are considered for competition use only.
KTM has redesigned the EXC chassis for 2017 with a new version of the no-link PDS rear suspension. Off-road guys still prefer this setup over the linkage-style design used on the competition bikes, primarily because of better ground clearance. In the front, a WP Xplor fork is used with good old-fashioned steel coil springs. The fuel tank is bigger than the motocross bike’s, but not that much bigger at 2.25 gallons. For that matter, the bike isn’t much heavier than the MX bike at 244 pounds without fuel and with mirrors.
Since the bike is supposed to be tamper-proof, here’s the big question: is it good enough in stock form? Yes! It’s actually a better dirt bike than the all-dirt 500XC-W that KTM left behind. Overall power and power delivery are both excellent. The EXC is very responsive at the bottom of the powerband just above idle. In the middle, it pulls as hard as any off-road bike sold, and only on top does it taper off early—at least, early compared to its closed-course brethren. It does all this with an exhaust note that’s quieter than that of the Yamaha TT-R125. The bike is so quiet that you hear lots of other noises that you wouldn’t otherwise notice. There’s a little chain slap and an odd humming coming from under the seat. That’s the reed valve. KTM’s claim that this design increases low-rpm output is probably accurate. The EXC makes power from the first crack of the throttle. It might even be a little too much, too soon. The only single-cylinder motorcycles that will out-torque a 500EXC are full-blooded street racers—the KTM 690 and Husky 701.
As far as fuel mapping goes, KTM engineers did a great job, but it’s clear that the EXC is lean. It has to be in order to get EPA’s blessing. Once in a while the motor will hiccup, and if you’re going slow, it might even stall. Overall, it’s not a big issue, but in cold temperatures, it can be worse. On hot days, on the other hand, the bike runs warm. That’s another trait typical of clean emissions and a quiet exhaust. This is effectively handled by a radiator fan. We haven’t yet ridden the bike in the full grip of summer, but we know that the competition bikes that use this motor can boil if you abuse the clutch or ride for extended periods at very low speed. This bike does have a six-speed gearbox, and gearing is pretty much spot-on for off-road riding, so there’s no reason to tax the clutch under normal circumstances.
We were a little surprised that KTM didn’t use super-tall gearing to help with the various certification tests. When you get the 500EXC out on the open road, it feels a little out of place. Most dual-sport bikes are geared so that 65 mph has the motor loping along at low rpm. Not in the EXC’s case. The KTM EXC motor spins fairly fast, the pegs vibrate and the wheels hop. There’s only one rim lock in each wheel, which throws them out of balance at high speed. In other words, the EXC feels like a dirt bike.
WAIT, WHAT ABOUT WEIGHT?
What puts the new KTM in a category above previous dual-sport bikes and perhaps most dedicated off-road bikes isn’t the motor, the mapping or the muffler. It’s the weight. That 244-pound figure is for real, and you don’t even need the stunningly accurate Dirt Bike super-scale to prove it. You know the KTM is as light as any four-stroke off-road bike from the first ride. It’s only a few pounds heavier than a Yamaha YZ450F motocross bike despite having an electric starter, a kickstand and all that street-legal stuff. Excess weight, as it turns out, is another one of those traits that have come to define dual-sport bikes and made us yearn to modify them. Now, KTM has done such an amazing job of trimming off pounds that there’s no way that you could do better. Virtually any aftermarket part you put on the bike will be heavier than the stocker.
Because it weighs about what a full-time dirt bike should weigh, the KTM handles exactly like a full-time dirt bike. It jumps, slides and turns about like it should. If you were to ride only dirt on this bike, the things you might want to change, and legally can change, are the tires and the suspension. The WP Xplor fork and shock are soft and cushy to an extreme degree. That makes for a comfortable ride when you’re on the bike for hours covering miles, but the suspension is too soft for anything but a casual pace. Inside the new fork and shock, most of the parts are smaller and lighter than those on WP’s previous open-chamber off-road fork, which means it will take more than a few clicks here and there to deal with hard off-road riding. You might have to go to stiffer springs and maybe even an experienced suspension tuner. As far as the tires go, we were surprised at how little grip they offered in mud and sand. Continental TKC80s have always been our favorites for adventure bikes, but on a bike as good in the dirt as the 500EXC, they are totally out of place. We used a set of street-legal Dunlop D606 knobbies for most of our testing and were delighted.
TURN KEY, RIDE DIRT
In the end, suspension and tires are the only things you should alter on the EXC. Then the bike is 100 percent ready for a national Enduro. You might break a blinker or crack a mirror, and that hanging part under the license plate will doubtlessly get sucked into the tire, but the bike’s performance is up to the task. Other modifications will only throw the bike out of balance and mess things up.
Well, there is one other thing that’s important to change—the way we think of dual-sport bikes.
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