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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).

CONTACT? 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 easier-to-ride powerband.


(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-midrange 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.

MXA RATING: 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.



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