We all know the story about Doug Henry and the arrival of the four-stroke in motocross at the end of the ‘90s. Chapter two of the story is just as interesting. In the April, 2000 issue of Dirt Bike we tested the second of the new-age four-stokes. It wasn’t a Honda, Suzuki or Kawasaki, either. It was the KTM 520SX, which was every bit as innovative as the Yamaha YZ400F. In that issue, we also tested the KTM 520EXC, which I rode in the Tecate Hare Scrambles. The cool part is that the KTM has stood the test of time better than the other four-strokes of that era. To this day, there are riders who will not stop riding their KTM 520s and 525s. Here are the two stories from that print issue of Dirt Bike.

The KTM 520SX was a legit four-stroke MX bike, long before Honda, Suzuki or Kawasaki got in on the act.


For two years, Yamaha has been parked in front of the free-lunch buffet, chowing down like there’s no tomorrow. The YZ400F has been the best bike in motocross, with virtually no competition. No other company has lifted a finger; it’s as if the Roadrunner reported to the Coyote’s den with a big sign saying “eat me, please.” The YZ has not only been the best four-stroke motocrosser in the business, it’s been the best motocrosser, period. How could Yamaha have taken the rest of the industry by such surprise?
KTM is the first major motorcycle manufacturer to refuse to be eaten alive. While Honda and Suzuki are sidestepping the issue by making four-strokes for other classes, KTM has stepped up and released its own four-stroke motocrosser. That might seem strange at first, but it really makes perfect sense. No one expected Yamaha to be as successful as it was, so they all got late starts when the four-stroke MX market suddenly came alive. KTM, being the smallest of the major players, was able to react the fastest. So now we have the 520SX, a bike that isn’t afraid to go head to head with Yamaha in the motocross world.

Spud Walters was one of the top riders in the Four-Stroke National championship. Normally, he rode a modified XR400. He would have loved to ride a KTM.

There’s one other player in the Yamaha vs. KTM war. Husaberg. Even before the YZ, the small Swedish company had been specializing in MX four-strokes, winning world championships with Joel Smets in the ’90s. But although the bikes were fast and light, they remained crude, expensive and obscure from day one. A few years ago, KTM purchased the struggling Husaberg firm with the express intent of learning how to build four-strokes. Not big trail thumpers like the LC-4 series that KTM already had, but racing four-strokes. So the plan was dubbed “RFS” just for that reason. Does that mean that the KTM is just a copy of a Husaberg? No, but KTM was able to benefit from all of Husaberg’s past mistakes. Instead of being a new-comer to the world of MX thumpers, KTM essentially has 10 years of someone else’s experience.

Much of the motor technology was gleaned from Husaberg.

Some of the technology in the new 520SX is very Husaberg-like, The head design and the clutch are so much like Husaberg parts that they might be interchangeable with a little work (might be; we haven’t tried yet). But on the other hand, the 520 has the look and feel of a much more refined product. The output shaft is on the left and the kickstarter is on the right, just like all of Japan’s products. The bike has a counterblancer that doubles as a centrifuge for separating oil from the air that exits the crankcase breather. The engine is dry-sump, but all of the oil is still carried in the cases, not in the frame like most dry-sump designs. And the top end has one cam. KTM might have a double overhead cam version in the works, but that’s for much later.
The biggest difference between the new KTM and previous European four-strokes is in the fact that it has some Japanese technology. The carb is just like the one on a Yamaha YZ400, and the ignition is also Japanese. Like the YZ, there’s a throttle-position sensor that affects the spark advance.
Once you look away from the motor, though, everything else is pure KTM. The chassis is just like the two-stroke version. It has a WP fork and a no-linkage WP shock. You get to the air filter though the side; the bike has a hydraulic clutch and Excel rims, all standard KTM items. The only component that’s different on the four-stroke is the handlebar, which is an oversize Magura. By the way, the handlebar mounts can be moved to any of four positions, front to aft.

Starting the KTM is just like starting any other modern four-stroke that doesn’t have an electric starter. There’s a certain feel that you develop. The choke is completely hidden under the fuel tank. You have to reach in and feel around for it. There is actually a great big hole in the tank that you use in order to turn it off. Flick the throttle once or twice, bring the kickstarter all the way up and kick smoothly all the way to the bottom of the stroke. There’s no need to find top dead center as long as you start from the top of the kick-starter stroke. That activates an automatic decompressor. Four-stroke guys won’t have a problem. Two-stroke guys will suffer for a few weeks until they become four-stroke guys.
Be prepared for a whole lot of power. The 520 is crazy fast. The bike makes super snappy power off the bottom and revs like nuts. There’s no place that the 520 doesn’t have tons of power. How does it compare to a Yamaha 426? It’s faster. It’s torquier. It revs higher. Are you scared yet? Don’t be. This isn’t like an overbuilt four-stroke from years ago. It’s very controllable. As long as you understand why the throttle is a twist grip rather than a toggle switch, you shouldn’t have trouble. Another big difference between the 520 and the big nasty four-strokes of the past is engine braking. It doesn’t have much.
The KTM has noticeably more flywheel effect than a Yamaha. The bigger engine gains revs more slowly, so when the wheel bounces off the ground, you don’t bounce off the rev limiter quite the way you do on a YZ. The KTM also has a little bit slower initial throttle response. It’s probably a good thing. With the extra power, you would have to be Super Rider to deal with YZ-level response.

There were two exhaust ports leading to a single muffler.

Yes, and you can feel it. The bike is 240 pounds with an empty fuel tank. That’s only seven pounds heavier than an RM250. It’s also narrower than just about any 250cc MX bike. The only thing that keeps you from flicking it around like a 250 is the fact that it makes a whole heck of a lot more power than a 250.
If you’ve ever ridden a KTM two-stroke then you already know pretty much how the bike handles. It has the same traits, some of which make Japanese bike riders a little uneasy. You have to be aggressive in the turns. If you enter a corner with the throttle off, it feels kind of tipsy and the front wheel doesn’t want to bite. But crack the throttle open just a hair at the entry to the turn and the bike feels like it’s on rails. And like KTM’s two-strokes, the front end has a little head-shake at speed. Despite that, it sticks to its lines well. It should; there’s a 510cc gyroscope in the cases that keeps you on track.
Here’s an interesting tidbit: We like the 520’s suspension better than that of any of KTM’s two strokes. We’ve always complained that the WP fork and shock feel soft on big stuff and stiff on little stuff. But the 520 doesn’t give us that feeling at all. In the rear, the linkless PDS system still has a progressive spring, but the action is surprisingly good in just about any kind of situation. The transmission shifts well even if it doesn’t have that many gears to shift into. The bike is a four-speed. We would have never known if we hadn’t clicked through the gears when the bike was on the stand. But we still don’t like four-speeds. It just means that you can’t use the bike for anything except MX. And the extra space in the cases isn’t used for stronger gears; there are just two empty spaces. You can retrofit the EXC’s six-speed if you want to.
We have to say we are amazed at how good the bike is. A year ago, if you told us that any bike would come along and make us forget about the YZ, even for a microsecond, we wouldn’t have believed you. But here it is, and already we have staff members who have proclaimed it a YZ beater. The majority of us won’t go that far without actually throwing the two bikes into a shootout. But it will be quite a battle.


Shane Watts rode our test bike the day before the 2000 Tecate Hare Scrambles and almost didn’t give it back.

They all hated me. We were waiting in the sand wash for the start of the Tecate Hare Scrambles. Rex Staten was on one side with his VOR 503. Gary Jones was on the other with a KTM 250. They both leered at me with disgust every time I did a practice start. It was going to be a dead-engine, straddle-the-front-wheel start, and I had a KTM 520 EXC with an electric starter. It really shouldn’t have been legal.
Normally an electric start bike wouldn’t be that big a deal in Tecate. The race is way too tough to carry around any extra weight whatsoever. Its terrain is best suited for a 125. Imagine 90 miles of trails so tight that you can’t shift into second gear for more than a few seconds at a time. The Los Ancianos MC just sends club members into dense brush with tweezers and saws for a month, and they come back with a 14-mile course. Then they run the top riders in the country around it six times, making for the toughest race in the west. The good news is that isn’t torture-tough or dangerous-tough. It’s fun-tough–if you’re riding the right bike.
I knew that the 520 wouldn’t be the wrong bike. But it sure didn’t seem like the perfect bike, either. It’s a big four-stroke, it has to carry around an electric starter and it makes more power than you could possibly need in that type of race. But I had ridden a prototype race version of the bike in Czecho late last year. I knew the bike was manageable in the tight stuff. And it should absolutely dominate the start.

Even to this day, a 2000 KTM 520EXC is competitive.

The 520 was developed in European racing. KTM had two teams, one racing prototypes in motocross and the other racing enduros. By the end of the season, they had not only developed a bike, but had won several world championship rounds in the process. Giovanni Sala even won the world enduro championship on the 400cc version.
The biggest difference between the motocross version and the enduro version is the electric starter. Both bikes have a counterbalancer which doubles as a device to keep oil from being lost through the crankcase vent. The balancer shaft is hollow and leads to the vent. When oil tries to go through the shaft, centrifugal force slings it out through little holes. It’s pretty smart. Other differences between the two versions are gear ratios, ignition, suspension valving, a battery and charging system and the usual enduro accouterments (lights, kickstand, 18-inch rear wheel).
There’s a lot of Husaberg heritage in the KTM. The clutch is almost identical to a ‘Berg’s, and so is the four-valve head. But then there is some Yamaha YZ400 in the bike too–primarily the Keihin carb, which is wired into a Japanese ignition. All of that is put together into a reasonably light package. We didn’t bring the fabulous Dirt Bike scale to Mexico with us for fear it would be confiscated at the border and used in the Mexican space program. But we know that the bike, electric starter and all, is about the same weight as a Yamaha WR400.

Shane Watts raced a 125 KTM at Tecate that year after a Dirt Bike photo shoot on the 520. He was, at the time, the best off-road rider in the world, as he proved at the ISDE in Melbourne.

I’m not sure if the rest of the guys in that sand wash knew all that. But they did know that I would get a good start. I’d have to be an idiot to mess it up (no comments, please). The flag dropped and while everyone else was running around their bikes and trying to find the kickstarters, I just pressed the button and threw a leisurely leg over the seat. Surprise! The bike wasn’t running, at least not right away. It takes about two revolutions of the motor before it fires up. In that time Jones and several other riders were able to get their bikes going. So the electric starter wasn’t that big a deal. But the motor was. Within about 30 feet, I had passed Jones. Halfway to the turn, I had passed the rest. The 520 wasn’t just a little bit faster than the other bikes. It was tons faster. In the deep sand, it ate up the 125 and 250 two-strokes with no trouble. There were very few Open bikes on the line (who would dare?), and those typically require a split second longer to come to life. I was long gone.
Of course there’s a reason the line wasn’t filled with KX500s. After about a half mile, the course funneled into a tight trail, and taking 50 horsepower and trying to keep it on a 12-inch-wide strip of dirt is a scary notion. I dove out of the wash and followed the narrow trail as it made a 180-degree turn. When it straightened out, I had the surprise of the morning; there was dust! Up ahead, I could see one rider with “Roeseler” scribed on his back. Larry had scouted the trail in advance and found a way to cut off the entire first turn. Yet another instance where old age and treachery overcomes horsepower and electric starting.

Even then we were impressed by the Brembo brakes.

Okay, I had a decent start, but the challenge was to avoid becoming a 520cc roadblock. The tight stuff at Tecate is as twisty as anything on the east coast. In many ways, it’s less forgiving, because the brush is much tougher than typical east-coast greenery. The branches don’t just push out of the way. They grab you and pull you right off the bike. In other words, it isn’t Open-class terrain. But that’s the best thing about the KTM. It’s fast but turns amazingly well. I don’t know of any motorcycle with Open-class power that is as manageable in the twisties. The power is easy to roll on. You don’t get tossed around by big bursts of acceleration and drastic engine braking. In fact, engine braking is less severe than it is with most 400cc four-strokes. And the bike is physically smallish by thumper standards. It doesn’t take long to get the hang of it and begin to feel like you’re the master.
On the flip side, there are still a lot of big spinning parts in that motor. And as any big-bike rider will tell you, those spinning parts act like a big gyroscope and resist any change in direction. You can really feel it when you suddenly have to make a right turn where you thought you were going to make a left turn, a very frequent mistake at Tecate. You don’t toss the bike to the opposite side. Instead, you wait until some invisible force releases you.
Another problem when you squeeze a big bike into a little space is the fear of stalling the motor. Throughout the race, I never let the motor stop with the exception of one time when I had to put the bike on reserve (about mile 40). But I was always worried about stalling it. Almost all of my braking was done with the clutch in. I wouldn’t let out the clutch until it was time to roll on the gas, usually right at the entry to the turn. Yes, my arms pumped up. But the KTM’s hydraulic clutch is at least a fairly easy pull. And to tell you the truth, so what if it stalled? One push of a button and I would be rolling again.
Throughout the course of the race, several other riders caught and passed me. I expected that. The course got rougher and rougher. I expected that, too. But I didn’t expect to get faster in the late laps. I thought the 520 would turn me into a rag doll. But it didn’t. I was able to hang on a little easier once I learned not to cut and thrust. I got an education in being smooth and easy. The suspension on KTM’s EXC line is perfect for tight trails. I imagine it would be too soft for fast speeds in the desert, but it couldn’t have been better for the sub-20 mph stuff that I had to deal with. When it was all over, I placed second to L.R. in my class. I figure that’s just like winning.
Is the KTM the ultimate woods four-stroke? Maybe. Frankly, you don’t need this much power for the woods, but it didn’t seem to hurt me. The Yamaha WR400 makes less power and is more demanding, the Honda XR400R is a little underpowered, the XR650R is overweight, the Husaberg line is still a little crude and the Suzuki DRZ hasn’t been around long enough for people to figure out how to get it into race trim. So as I see it, there’s only one other four-stroke right now that can give the 520 a run. That’s the KTM 400, which we get to ride next month. Can’t wait.

It’s hard to be photo-ready after the Tecate Hare Scrambles. The shoulder is a souvenir from the previous year there.


See you next week!

–Ron Lawson

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