March 24, 2014
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WHAT IS IT? This is a three-prong exhaust:(1) Since it is a slip-on system, it is less expensive than buying a full system—although buying a titanium slip-on does bite into the budget more than a stainless or aluminum slip-on. (2) The object of a single-sided 2013–’14 CRF450 exhaust pipe is to avoid the complexity and weight of the stock dual-exhaust system.(3) It increases midrange power and throttle response over the stock CRF450 pipe.

WHAT’S IT COST? $599.99 (Ti mid-pipe, Ti canister and Ti end cap), $599.99 (Ti mid-pipe, Ti canister and carbon end cap), $499.99 (stainless mid-pipe, aluminum and carbon end cap). As an added bonus, FMF includes a special UFO side panel that eliminates the bulge on the left side of the CRF450.

CONTACT? or (310) 631-4363.

WHAT STANDS OUT? Here’s a list of things that stand out with the 2013 single-sided FMF Factory 4.1 Honda CRF450 slip-on exhaust.

(1) Design. Even though it is a slip-on, the FMF Factory 4.1 muffler still has a built-in resonance chamber. The chamber and its shape cut down on noise while allowing for a shorter overall canister length. The end cap, whether stainless or titanium, incorporates a snap-ring feature to secure optional inserts.

(2) Single-sided. What are the downsides of twins?  (A) Weight. A twin exhaust adds several pounds of unnecessary weight. (B) Complexity. In a sport based on rugged simplicity, extra parts are counterproductive. (C) Cost. Dual exhausts cost more to manufacture, thus raising the retail price of the bike. (D) Crash damage. With mufflers on both sides, the odds of damaging the pipe in a crash go way up. (E) Width. The dual mufflers make the back of the CRF450 look like a Kardashian sister doing the rumba.

(3) Performance. In stock trim, the 2013 Honda CRF450 is mild and mellow. Its best feature is its solid, low-end throttle response, but there are diminishing returns as the rpm climb. On the dyno, the FMF Factory 4.1 increased peak horsepower by 1-1/2 horses. On the track, this power gain was most noticeable from 6000 rpm to 9300 rpm. After 9300 rpm, the FMF Factory 4.1 fell off more than the stock exhaust; however, as most CRF450 owners know, after 8400 rpm, it is time to shift anyway. The extra midrange power made the CRF450 feel livelier down low and gave it the extra burst it needed to get on the pipe sooner.

(4) Stinger inserts. The MXA test crew ran the Factory 4.1 without any inserts, but FMF offers both sound and spark arrestor inserts that snap in place.

(5) UFO side panel. Every test rider loved the special UFO side panel, because it eliminated the irritating bulge the riders felt when they leaned back.

WHAT’S THE SQUAWK? With a slip-on, the performance is limited by the dimensions of the stock head. There is more power available with a full FMF system.


It offers more power, is less expensive, weighs less, is easier to maintain and looks cleaner. Honda’s engineers should have thought of this. 


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