PRODUCT:  The Scary Fast Grunt is a tapered exhaust flange for the KTM 450, 350 and 250 four strokes. The goal of the Grunt targets controlling and enhancing the bottom roll-on power. We tested the Grunt on a KTM 450SX-F that uses a large header where it exits out of the cylinder and this high-flow design tends to let power snarl, rather than the flow. Scary Fast came up with a way to smooth the response, let it roll-on sooner and all together make the hit more useable via their tapered exhaust manifold, the Grunt. The hard anodized aluminum unit was designed with a dimension and taper between the cylinder and the pipe that helps the stock header act like it has more taper, which effectively smooth the blast, and lets it roll out just a faction earlier than stock.


POSITIVE:  Strong results here. Installation requires you to remove the header/mid pipe and then remove the stock exhaust manifold. Fit on the Grunt, and then refit the pipe. It seems quite mysterious that this small device can actually alter the powerband in a positive manner, but it does. It's not earth shattering, more like subtle and smooth bending the violence of the stock 450 into a smoother, sooner feel to the powerband. This additional roll-on helps traction, the ability to short shift and our ability to smoothly attack the track.

            We also tested it on an FMF system (Mega Bomb/4.1) and it worked well. The FMF system already has a more tapered header section that helps to broaden the hard hit, but the Grunt piggybacks with it and gives it a even lower pull that is strong, yet tractable.



BOTTOM LINE: Very positive here, especially with the stock header. While it won't bring the 450 SXF into the enduro lug zone, it does soften and broaden the hard edge hit of the stocker. Since this initial test we slipped one onto a 2012 350SX-F and came away positively pumped with bottom power enhancement. More on this later!


CONTACT: (480) 399-8601

You can see the size difference between the Grunt and the stock exhaust manifold. The Grunt's internal
 taper helps improve bottom power.

The Grunt doesn't take long to install, but helps smooth and lower the hit on the 450.

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WARNING: Much of the action depict­ed in this magazine is potentially dan­gerous. Virtually all of the riders seen in our photos are experienced ex­perts or professionals. Do not at­tempt to duplicate any stunts that are be­yond your own capabilities. Always wear the appropriate safety gear.

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