Repacking is essentially packing the muffler can with sound deadening material. The most common material is fiberglass, but there are other types of packing...everything from ceramics to steel wool to the fiberglass insulation from one's attic. Of course, I would advise only using commercial motorcycle-specific products.
The frequency of repacking motorcycle mufflers is dependent upon a number of variables. High compression 2-stroke mx racers may need a repack between every moto. However, most trail thumpers like my KLR600 should get at least a year out of the packing, even with a aftermarket can.
When I purchased the KLR600, I repacked the muffler mainly because it was loud. It was about 40% degraded, which essentially means that 40% of the packing broke down and got blown out the back. While I normally use fiberglass packing materials, for some reason I decided to experiment with a ceramic material after doing some research. The product was:
Thermal Zerom, MPK1 Ceramic Muffler Packing Mat (12" x 24")
My Blog Post entitled Supertrapp E.A.R. Series chronicles the initial repacking from June 2019.
The following video shows my repacking in May 2020 at +1,581 miles following my first packing.
In short, I unexpectedly found the ceramic packing had deteriorated and all of the fibers had blown out the muffler. This isn't to say I got 11 months and 1,581 miles out of the ceramic packing. On the contrary, based on when I started to sense the decibel level on the rise, I'm guessing that the ceramic packing started immediately deteriorating under the back pressure and was probably gone at +750 miles. I can't be 100% sure as there's no window to look in on things, but that's what I'm guessing.
Anyway, I'd already decided to go back to the gold-standard fiberglass packing material so, unfortunately, I really didn't learn my frequency of repacking for the vintage KLR with it's aftermarket can. That will come. Stay tuned.
