WHAT IS IT? The Factory 4.1 with MegaBomb head pipe is FMF’s premium exhaust system for the new 2013-14 KTM 450SXF. Several KTM support and offroad teams run the 4.1.

WHAT’S IT COST? $949.99 (full system with MegaBomb head pipe).

CONTACT? or (310) 631-4363.

Here’s a list of things that stand out with FMF’s KTM 450SXF Factory 4.1 exhaust.

(1) Models. FMF makes three versions of the Factory 4.1 for the 2013-14 KTM 450SXF. MXA tested the RCT anodized full system with the carbon fiber end cap. It is constructed from titanium, the canister is anodized blue, the end cap is carbon fiber, and the head pipe offers MegaBomb’s Resonance Chamber Technology (RCT). For $50 less, you can order the Factory 4.1 with Ti end caps with the option of anodized blue or natural Ti canisters.

(2) RCT. FMF’s Resonance Chamber Technology (RCT) consists of the MegaBomb resonance chamber in the head pipe mated to a specially shaped muffler core. Resonance chambers not only help lower sound levels by approximately 1 dB, they also allow for a shorter overall tuned length of the system, which means more centralization of mass and a reduced risk of crash damage.

(3) Performance. In stock trim, the 2013-14 KTM 450SXF has a luscious powerband. Not only does it make lots of horsepower, but the power is smooth and easy to use. The 450SXF powerband starts off mellow and builds power incrementally as the rpm increases. It is a do-it-all style of power. But, not every rider is looking for ease of use. Most MXA test riders wanted the 450SXF to hit harder down low, pull stronger through the middle and rev faster on top, and that is exactly what the FMF Factory 4.1 did. With extra horses, the test riders had more usable power, and they had it both sooner and later.

(4) Fit. The three-piece FMF Factory 4.1 system slipped right in place. The fit was tight between the frame and the shock reservoir, but thanks to FMF’s separate midpipe, there were no issues.

(5) Sound. With increased packing volume in the irregular-pentagon-shaped canister, plus quiet inserts and a removable spark arrestor screen, the FMF Factory 4.1 can pass all the current sound tests. The MXA wrecking crew preferred to run it in its 94 dB configuration for increased midrange.

WHAT’S THE SQUAWK? No complaints.

Thanks to collaboration with KTM’s offroad, support and amateur teams, the Factory 4.1 full system is an excellent exhaust for the 450SXF.

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