Just like the motor in the 2016 KTM 450SX-F motocross
bike, the new 500EXC motor has a single-overhead-cam
layout, but the whole engine is more compact and lighter than the one it replaces. To give it a displacement of
510cc, the stroke is 8.6mm longer. It has a new 42mm
throttle body and a Keihin injection system, but the mapping is said to be locked in the approved setting. All of
the emissions equipment is invisible. There’s no air pump
hanging off the side of the motor like on a Honda XR650L,
and the evaporative canister is hidden within the frame.
The bike also has some fairly extreme features to deal with
noise restrictions, beyond the muffler itself. KTM engineers
placed a reed valve between the air filter and the throttle
body to silence intake noise. Even the Continental tires
were selected to minimize noise in a drive-by sound test.
The gearbox is a six-speed, and the diaphragm-spring
clutch is hydraulically activated.
KTM is keeping the PDS rear suspension on the EXC
line, so there’s no linkage to limit ground clearance. The
WP Xplor shock is new this year and is another source
of weight loss. In front, KTM has its new two-spring WP
Xplor 48 fork. This version has no preload adjuster but
does have topside clickers for compression and rebound
It all comes together in an amazing overall package.
First things first: the bike weighs 244 pounds with an
empty tank on the fabulous Dirt Bike scale. That even
includes the mirrors. To put that in perspective, a Yamaha
YZ450F motocross bike is only 8 pounds lighter. The electric-start YZ450FX is 7 pounds heavier, and the dirt-only
KTM 500XC-W from last year was 5 pounds heavier. So,
already the EXC has cleared the first big hurdle to being
considered a legitimate dirt bike. The new EXC’s power
is outstanding. It’s so quiet that it’s misleading. The noise
level can be drowned out by an electric weedwacker. You
can easily be sucked into grabbing too big a handful of
throttle. Throttle response off the bottom is instantaneous,
almost jerky. Higher in the revs, you don’t get the outrageous output that you do on the competition models,
which is quite reasonable for trail riding. Any more and it
would just be showing off. It’s interesting that KTM geared
DUAL-SPORT COMPARISON The 500EXC is a brute that weighs far less than any dual-sport bike to make this kind of power.