Husqvarna FMF Q4 Muffler and Megabomb Header Review

Cycle News Staff | June 15, 2020

FMF is synonymous with off-road racing and KTM/Husqvarna’s championship-winning efforts, in particular. We’ve always been a fan of their quieter, Q-series mufflers and Megabomb headers. The system we chose for our Husqvarna FE 350 test mule is the latest Q4 Hex muffler and Stainless Steel Megabomb header.

Husqvarna FMF Q4 Muffler and Megabomb Header Review
The aluminum muffler and stainless-steel headerpipe might not be as light as titanium but are ultra-strong and durable.

These components are the workhorses of FMF’s exhaust lineup and built of robust stainless-steel (header) and aircraft-grade aluminum (muffler). Keeping this bike quiet is a priority. FMF claims max sound output is 96dB. (We don’t need noise to be fast!) This bike has a fairly restrictive emissions system, so, to keep the system fueling properly, an exhaust that aligns more with stock is a wise choice. The Q4 comes with a removable spark arrestor (held in by a retainer clip) and quiet insert. We kept both in place for this evaluation.

Husqvarna FMF Q4 Muffler and Megabomb Header Review
The FMF Muffler and Megabomb headerpipe come right out of the box with everything you need for mounting.

Husqvarna FMF Q4 Muffler and Megabomb Header | Lowdown

Standout Feature: Developed tightly with Husqvarna Factory Racing efforts, FMF systems should be the perfect choice for those looking for an exhaust upgrade on any bike in the lineup.

MSRP: Q4 Muffler: $389.99, Megabomb Header: $474.99

wheelie-up High-quality materials and craftmanship look as good as they are.
wheelie-up Effortless install with intelligent componentry and design.
wheelie-up FMF supports numerous off-road racing and riding initiatives so they’re easy to support with your money.
endo-down Almost $900 as tested

Husqvarna FMF Q4 Muffler and Megabomb Header Review | Rider Analysis

The first step in evaluating an exhaust system is installation. And there have been nightmare-ish KTM/Husqvarna steps in the past to get mid-pipes and headers removed/installed. Thankfully, that job is no longer an issue, as the 2020 bikes allow easy stock-system removal. Likewise, the FMF Megabomb header comes in a header and mid-pipe setup so you can simply thread it through the chassis.

The only slightly complicated part of swapping the header system is re-routing the exhaust sensor. The stock header pipe locates the sensor in front of the cylinder, highly visible, and somewhat vulnerable to breakage. The FMF system smartly tucks the sensor behind the frame, inside the rear of the engine compartment, completely protected and barely visible. You’ll need to loosen the tank and route the sensor cable to the rear of the engine. That’s the extent of the install complications.

Husqvarna FMF Q4 Muffler and Megabomb Header Review

The FMF unit comes with all the hardware you need to install it except for the frame-mount grommets and collars. You will re-use the stock aluminum collars and rubber pieces. These are easy to pop in and out with a dull screwdriver or punch. Keep their orientation organized and slip them back on just as they come out. It’s simple and if you have leftover parts, try again.

The whole system lines up well and the supplied spring retainers are a welcome part of the complete job. They have cool rubber covers that provide a nice clean finish. The muffler also shares the stock grommets and collars.

If you start with the header, move to the mid-pipe and then the muffler, slipping the system together along the way and waiting for everything to be connected before you tighten frame mounts, you should have an easy install. If you find the pieces aren’t sliding in, don’t be scared to apply a little light spray lube. But keep all the bolts loose until the end.

Husqvarna FMF Q4 Muffler and Megabomb Header Close up
Husqvarna FMF Q4 Muffler and Megabomb Header Review

You’ll notice this isn’t an ultra-light system right away. And that’s fine. We’re not overly concerned with saving weight; we really just want a little more bark in this beast. The quality of the construction is more appealing to us. We weighed complete systems back to back and the stock stuff is around a pound heavier as tested.

The FMF system maintains a low overall sound level, but the exhaust tone and crackle are definitely different and more aggressive than stock. And the bike felt like it gained power where we wanted it—on the lower-end of the range, especially right off idle. The differences aren’t mind-blowing, but it’s nice to have a little more from the stock powerplant. It’s here we feel the FE lineup needs the most massaging and our exhaust upgrade seemed to start the process nicely. CN


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