WHAT IS IT? The FMF Factory Fatty takes on the look of
the old cone pipes that were once used by factory teams,
while the companion Gnarly pipe is built for durability
with a distinctly different powerband. The Powercore 2.1
silencer is new technology for the two-stroke market.
WHAT’S IT COST? $249.99 (Factory Fatty, Gnarly
pipe), $399.99 (titanium Powercore 2.1 silencer), $199.99
(Powercore 2 silencer).
www.fmfracing.com or (310) 631-4363.
WHAT STANDS OUT? Here’s a list of things that stand
out with the FMF Factory Fatty and Gnarly pipes, with
the Powercore 2.1 silencer for the 2017 Husqvarna TC250
and KTM 250SX.
(1) Installation. O-rings don’t stand the test of time.
The last thing you want to deal with when buying an
aftermarket pipe is discovering that your bike’s O-rings
are damaged. We applaud FMF for including fresh O-rings
with each new pipe. So, before mounting your new FMF
pipe, make sure to install the new O-rings, even if the old
O-rings look fine. Both the FMF Gnarly and Fatty pipe
mounted with the Powercore 2.1 silencer with ease.
( 2) Stock trim. The powerband of the 2017 KTM and
Husqvarna 250 two-strokes can be summed up in one
word—intense! This stock power hits incredibly hard in the
midrange, which tends to break the rear end loose if you
aren’t on alert. Then, not long after, the excitement is over.
Don’t get us wrong, we like the jolt of a good two-stroke
blast, but we want more after the thrill is gone. Most MXA
test riders think that this beast needs to be tamed. Oh,
don’t get us wrong; we don’t want to slow it down, we
just want broader power across the board. Note: Before
we put on the pipes, we turn the power-valve adjuster all
the way out, then in 1 1/4 turns.
( 3) Factory Fatty. The first thing we noticed with
the Factory Fatty pipe and 2.1 Powercore combo was the
smooth bottom-end. Around tight corners, roll-on power
was smooth, and there was enough power that it didn’t
have to be aided by using the clutch. The midrange was
more powerful than stock, but not by much. With the
added bottom-end, the transition to the midrange wasn’t
as explosive. It allowed the rear wheel to track better
across the ground. At the top-end, the Factory Fatty
kept on pulling and didn’t sign off as early as the stock
pipe. The FMF pipe/silencer combo didn’t lose ground
to the stock pipe anywhere on the curve; it only gained
power and lengthened the powerband. The pipe did this
by increasing bottom and top significantly to bridge the
already-powerful midrange. It produced a faster and easi-
( 4) Gnarly. The Gnarly pipe is a 1/2-pound heavier
than the Fatty, thanks to its thick 18-gauge steel construction (the Factory Fatty uses 20-gauge). The thicker steel
is designed to take a beating from roost, logs, rocks and
ruts. It should be noted that FMF’s Gnarly powerband
is distinctly different from the Fatty’s. The Gnarly offers
better bottom-end than the Fatty and a quicker transition
into the midrange. The midrange hit is still rather hard, but
the increased bottom makes the transition from low to mid
less abrupt. Once it reaches the top-end, the Gnarly signs
off fast. This is a pipe for riders who prefer bottom-to-mid-range power and for riders who ride tight trails, GNCC
races, woods, desert or WORCS events.
WHAT’S THE SQUAWK? Both pipes have distinctly
different power characteristics. Pick your poison. The Fatty
tames the stock powerband, while the Gnarly gives up top-end for a potent bottom.
Both these pipes blew the stock Austrian
250 pipes out of the water. For fast tracks,
every MXA test rider chose the Factory Fatty
pipe. The Gnarly is best suited for riders
looking for more durability and more usable
power on tight trails or skilled motocross
riders who don’t depend on revs. The 2.1
Powercore silencer worked superbly
on both bikes.
FMF 250SX & TC250 FACTORY FATTY & GNARLY
MXA TEAM TESTED