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The Lone Wolf
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KTM 520 SX
Jeff Buchanan
12/01/2006
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Photography by Cordero Studios/corderostudios.com
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 In the late 1990s, Lance Smail was a lone
wolf competing in the vaunted AMA Supercross championship series on this Tom
Moen-prepared, four-stroke powered KTM. By virtue of being the sole four-stroke
in a series populated exclusively by two-stroke machines, Smail and the KTM were
instant outsiders. However, at every stadium the bike appeared, the fans went
crazy for it. In a field of buzzing, shrieking two-strokes that sounded like
agitated bees, the distinctly aggressive thumping of the KTM, with
its signature backfire, made it a crowd favorite. (Click image to enlarge)
At that time, the use
of four-stroke technology in off-road motorcycling, due to the relatively
complicated and heavy workings of valves, camshafts and timing chains, had
pretty much been relegated to recreational use. Naturally, when the one-off KTM
lined up next to the all-conquering two-strokes in their sacrosanct domain of
Supercross, it bordered on being little more than a sideshow.
 All that
changed on March 8, 1997 at the Daytona International Speedway round of the
Supercross series. Smail piloted the misfit KTM through a field of the nation’s
top professionals on the infamously rugged in-field course and it became the
first four-stroke machine to qualify for an AMA Supercross main event. After
decades of dominance by the ubiquitous two-strokes, it was a noteworthy
achievement and a portent of things to come, and very few understood its
significance at the time. Legislation had been steadily evolving to address the
growing concern about the environment—two-stroke powerplants, notorious
polluters, were put on notice that their days were numbered. (Click image to enlarge)
To help put it
in perspective, internal combustion engines have four basic phases—intake,
compression, power and exhaust. Four-stroke engines require four strokes of the
piston in order to accomplish the process (hence the name), with a power stroke
being generated every two revolutions of the crankshaft. Two-strokes, through an
ingeniously simple design of integrated transfer ports in the cylinder walls,
combined with the science of back-pressure generated by the exhaust system, are
able to achieve the essential intake/compression/power/exhaust phases in
just two strokes of the piston, thus producing a power stroke with each
revolution of the crank. The design eliminates the need for intake and exhaust
valves, camshafts, and timing chains. As a result the engines possess very high
power-to-weight ratios.
Unfortunately, the very heart of the two-stroke’s
engineering necessitates the lubricating oil for the piston and top-end be mixed
with the gasoline. This in itself presents obvious problems with regard to air
pollution; as a two-stroke spews burnt oil directly into the atmosphere. More
damning still is the fact that two-stroke engines are not very efficient. Even
the best-tuned units will lose a percentage of this gas/oil mixture, completely
unburned, due to an unavoidable degree of seepage from the exhaust port. The
fallout? Two-stroke engines are going the way of the dinosaur. In their place a
new breed of high performance, cleaner burning four-strokes have taken over the
racing world. However, the motorcycle pictured here earned its place in the
annals of Supercross as being the first.
 This early four-stroke project was
a Frankensteinian task. Working with
limited resources, designer and race
mechanic Moen cut and sawed,
fabricated and welded bits and pieces from various
KTM race bikes to
create a competitive, lightweight chassis to cradle one of the
Austrian
brand’s existing four-stroke engines. (Click image to enlarge)
The somewhat antiquated
motor, borrowed from one of KTM’s more sedate enduro models, was bored out to
538cc to make full use of the AMA’s displacement allowance for four-strokes.
Every aspect of the engine was modified to achieve the kind of performance
necessary to go up against the exotic machines in the competition’s arsenal. A
lighter clutch was installed and a full pound-and-a-half shaven off the bulky
crankshaft. In the end, the motor produced enough power to eliminate the need
for the low-end pull of first gear, as well as the seemingly endless top-end
available in fifth, so they were pulled out to save weight, making the bike a
three-speed. With prodigious use of lightweight parts they were able to get the
bike’s overall weight down to 243 lbs (compared to an average of 220 for the
competition).
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