After Ratty's first "long" ride (20 minutes) I noticed the muffler was rattling around a little, and it got louder. So I uncliped the end cap and pulled out the guts. This is what I found:
The packing was hard and crumbled:
I decided to go ghetto, and used some superfine steel wool pads I had:
I wrapped the perforated core and then bound it all with some rusty mechanics wire:
It somehow managed to slide down into case with no wiggle room. I have no idea how loud or quiet it is, as I didn't care to fire over the beast at 8pm in the garage.
I have no idea how long this will last. It could very well blow apart the first time I run down the road, and I've heard excellent stories about the steel wool shooting out the back of a muffler glowing red hot. Luckily, I won't be taking Ratty on any off-road adventures.