Dear Mr. Know-It-All,
Recently, over the past couple of rides, my WR450F has gotten noticeably louder. The bike has an FMF Q4 that is a few years old but has no damage to it. Has something come loose inside of it, like the core or a baffle?

Baffled in Bishop
Via [email protected]


Not that I want to rant, but kudos to you—one, for using a system that is both legal and attempts to lessen the throb that a big four-stroke belches, and two, for wanting to perform maintenance on an incredibly crucial part of your machine. While a four-stroke puts out good, usable power that a trail rider craves, the decibel level of a blown-out exhaust can is catastrophic to our cause. The axiom “less sound equals more ground” is absolutely on point, as we want to share the trails with mountain bikers, e-bikers and hikers, and not have them turned off by the racket of a big-bore thumper as it shakes pine needles off tree branches. 

There is nothing wrong with your silencer, but the packing inside gets cooked. Over time, and with the heat of the engine, the packing becomes brittle, breaks up and gets loose, letting the sonics bounce out of the core and into the can instead of flowing into the packing and being absorbed. Replacing the packing isn’t a quick and easy job, but it will not only help keep the exhaust volume down, it will help maintain proper power. FMF sells replacement packing for its systems. FMF Racing’s Premier Packing kit is made up of four layers to improve performance and provide long-lasting results. There are instructions on FMF’s site that walk you through the job.

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