MO Maintenance: Repack Your Muffler

John Burns
by John Burns

The price you pay for the extra performance and light weight of aftermarket-exhaust liberty is internal vigilance. You’ll need to repack your muffler with new, ahh, packing material now and then. Unlike your typical stock exhaust, which is built to last a lifetime with muffler baffles made of steel and other solid metals, most performance pipes are packed with fiberglass-like packing stuff that uses itself up over time, reducing performance as it gradually blows out the tailpipe, and producing more noise. I remember this full-race Akrapovic system being surprisingly quiet when we put it on here, how long has it been? About five years ago. Lately it seems like it’s gotten considerably louder, but that could be because all the new bikes I bring home seem to be getting progressively quieter? Anyway, repacking this thing is a good way to see how it’s done.

There are plenty of videos on Youtube how to do this, but my experience is that no two mufflers are put together exactly alike. If you’re lucky, your muffler is held together with bolts you can simply unscrew. My Akrapovic uses rivets (lighter and cheaper), and so you need a drill to remove them, which isn’t too difficult once you find a bit that still drills.

I’d hoped to just remove the cap from the other end, but it wasn’t meant to be. But aluminum rivets are easy enough to drill out. The great Ron Griewe, RIP, introduced me to cutting oil. I never have any that I can find, but a little squirt of WD-40 or something to lube things up does make drilling easier.

I assumed after I drilled out the four rivets holding on my end cap, I’d be able to pop the cap off without much trouble, but that was not the case. Far from it in fact. I rode the bike for a couple months that way, hoping the exhaust pressure, vibration and heat might blow the end cap loose if not off (hopefully on a nice quiet street where I could backtrack and pick it up). No dice. Apparently there’s a bit of high-temp adhesive in there also: Facing reality head-on, I hit it with the trusty Sears MAPP torch, which made the end cap at least budgeable when tapped with a rubber mallet.

I pity the fool who doesn’t keep one of these around the house. Heat conquers all.

From there, it required quite a bit of wiggling, cursing, and tapping with a rubber mallet before I finally got the end cap off. In dreams, I’d hoped to just yank the end cap off with the muffler still on the bike and repack the thing from the rear, but that clearly wasn’t going to happen. I wound up having to remove the muffler and take both ends off the can. Typical. Akrapovic really does a nice job; both end caps are a seriously tight, precision fit.

A little aluminum foil may or may not have kept the can from discoloring when I hit it with the MAPP torch, which finally loosened the end cap up enough to remove it.
The end caps of my Akrapovic are a very snug fit indeed, and without the aid of a nice soft, yet stern, mallet, I would’ve never gotten them out. Old beach towels and rug kept scarring to a minimum. Note lead pipe for leverage.

As it turned out, of course, the internal steel baffled core of my muffler was attached to the opposite end cap, the engine-side one, and I might’ve been able to do all this without removing the dang end cap at the exit. Live and learn.

Remarkably simple yet fiendishly cruel.

Assembly is a reversal of disassembly.

Here’s the stuffing that came out – actually not looking as bad as I thought it would. Gloves aren’t a bad idea handling this stuff, which is kind of fiberglassy but not too nasty.
You can buy exhaust packing at bike dealers, online, wherever. There’s the blanket style stuff pictured here, and there’s the loose stuff like what came out of my pipe. Was I going to order up a bag of the loose stuff and wait a few days to do it right? Hell no. This 18-inch FMF blanket looked like it would work, even though it’s about an inch short… and it was like half the price of the Akrapovic item.
Just wrap her around there like a diaper, use a little masking tape to hold in place, and shove it back into the canister…
I fell in love with the pop rivet in shop class, circa 1974. This old tool broke, but I needed to go to Harbor Freight for different rivets anyway, where I got a new tool and rivets package deal for $4.99. Also 29 new titanium drill bits for $16.99!

It was kind of a bummer getting the upstream end cap back in and the holes aligned, but I got her done and freshly riveted, and was admiring my work when I noticed the stainless steel accent strip lying there on the floor that should be wrapped around the can and held on by the same four rivets. Drilled them out again, put on the accent piece, et voilà!

I knew we were going to come up short, but no big deal really, as I stuffed some of the loose packing material chunks from before that were still in good shape.

When I went to put the other end cap on, it re-occurred to me that the core inside my pipe doesn’t run right through the middle of the can, but more through the top half of the oval canister, and that I should’ve wrapped the blanket around the core in kind of an offset manner to accommodate that reality. The blankie wasn’t nearly as squishy as I expected it would be, and I couldn’t slip the business end cap over the core and into position dammit. Soon I knew what I had to do: Drill out the four rivets yet again (easy with my new bits!), pull out the end cap with attached core (still not easy), and rearrange the blanket so it was one thickness where it needed to be, and three thicknesses on the bottom side. Perfect!

Ahhhh, much better. If you squint your ears just right, my repacked Akrapovic full-race system sounds a bit quieter than it did. A very little bit quieter, and not much louder than a WW2 bombing raid on a ball-bearing factory.

Luckily, I’m only a little embarrassed, since there are tons of big V-twin cruisers around that are way louder than my R1. And it’s kind of cool to have an old carbureted dinosaur around, a survivor from the pre-catalytic converter days. It’s not just amazing how much faster motorcycles have gotten in 20 years, but that they’ve also gotten quieter and greener at the same time. I’ll keep this one around to remind the neighbors and kids how much better they’ve got it now.

Most sources say a streetbike like mine needs new stuffing every 5 to 8000 miles. At the rate I ride this bike, if I’m lucky I’ll never have to do it again.

John Burns
John Burns

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5 of 33 comments
  • Old MOron Old MOron on Sep 17, 2018

    Jeeze, how many times did you have to uninstall and reinstall the rivets?
    That's why I hate working on my bike.

    • See 2 previous
    • Alaskan18724 Alaskan18724 on Sep 17, 2018

      Measure six times, cut once. Repair, reassemble, repeat. The mission statement in my garage.

  • Jefflalone Jefflalone on Sep 17, 2018

    "most performance pipes are packed with fiberglass-like packing stuff"

    The stuff I just got even says "R-13" right on it!