RUN LIKE A KTM
Unless you’ve been living under a rock, you know that the MXA wrecking crew has been harping on Husqvarna to make its FC250, FC350 and FC450
run as crisply as its almost identical KTM brethren. All
of our plaintive cries have fallen on deaf Austrian ears,
thus we have been forced to make the necessary mods
that Husky’s engineers refuse to make. In stock trim, the
Husqvarna and KTM deliver their power with a uniquely
different feel. The Husqvarna has muted low-end throttle
response, while the KTM is more responsive and more
alive off idle. On the dyno, both of these engines make
their peak horsepower as close to peak rpm as possible.
Thus, having slower throttle response isn’t a damper on
peak horsepower. But, if you start slow, it is going to take
longer to get up to speed—and that defines the big difference between the Husky FC250/350/450 and the KTM
250/350/450SXF. The KTM jumps up into the meat of its
power quicker, while the Husky delivers a steady vibrato
of power. They both make big horsepower numbers, and
they are both flat-out powerbands. If you aren’t revving the
KTM or the Husqvarna, you aren’t getting all it has to give.
Most MXA test riders prefer the KTM’s snappier throttle
response and quicker rev, but “most” is not all. On the other
side of the coin, there are Vet riders who find the metered
delivery of the Husqvarna FC350 to be more usable in
off-cambers, ruts, concrete starts and tricky switchbacks.
But if push comes to shove, we think the KTM powerband
is racier—and these are race bikes.
It is important to note that there are no cam, valve,
piston, throttle body, fuel pump, case, ignition or crank
differences between the 2018 KTMs and Husqvarnas.
They share the exact same mechanical parts, which begs
the question: “Where did the throttle response go on the
Husky?” The answer? It’s not the engine that mutes the
Husqvarna’s powerband, it’s the parts that are downstream
from the engine. Culprit number one is the Husky’s plastic
airbox. Suspect number two is the choked-up, ice-cream-cone-shaped restrictors in the FC350 and FC450 mufflers.
Third in the lineup is the tall gearing. Fourth on the wanted list is the backfire screen. We took our 2018 Husqvarna
FC350 and put it on MXA’s easy-peasy hop-up plan.
THE HUSQVARNA AIRBOX
The simple fix is to drill holes in the Husqvarna airbox
covers. Motorcycle engines are air pumps. They draw air
in, combust it with fire and blow it out the exhaust pipe.
The more air you draw in, the more you can blow out. The
byproduct of all of the sucking and blowing is horsepow-
er. The Husqvarna’s plastic airbox suffocates the intake
of fresh air into the Husky engine and is detrimental to
throttle response. Thus, the identical engine, equipped
with a KTM airbox, is snappier and more responsive. This
is where Snap-On, Makita and Dewalt come into play.
Break out the drill. But, it is not as easy as it sounds. We
conferred with the Rockstar Husqvarna team to find the
correct way to open up the plastic airbox. Where you drill
the holes is as important as drilling them. Step one is to
remove the right-side panel. This exposes the right side of
the airbox. We cut the airbox open with a box cutter. The
plastic on the sides of the airbox is very thin. Rockstar
Husky recommends removing the airbox from the frame
and trimming as much of the interior plastic obstruction
away as possible; however, you can just cut the exterior
side out to get more air in and keep dirt and water out.
With the right side of the airbox opened up, we marked
where the straightest shot into the airbox was on the right-