Choosing a muffler

Hey, MG, muffler choices are plenty and it depends what you are after. Quiet riding or more performance. Our sponsor vendors have all you need. Try reading through some of the muffler threads here and you will get an idea. Many folks modify the stock muffler to increase performance a bit and still remain relatively quiet. Here's a link to explain expansion chambers which are not mufflers but an exhaust system performance part. It would go between the muffler and the cylinder. They need to be a specific shape and distance from the cylinder to make them work for your needs.

the stock muffler is about the quietest but you could custom fit any muffler you like to make it even quieter

https://en.wikipedia.org/wiki/Expansion_chamber

One option is getting a used muffler off a 60 to 125cc dirt bike as these are about the right size that they'll slip over the stock pipe and can be brazed, welded, or even clamped to the pipe. These will quiet things down some but be free flowing at the same time. I would run enough pipe to put the muffler behind you and then point the outlet down which will help quiet the bike even more. It'll be louder than the stock muffler but considerably quieter than no muffler at all

Dave, I just made a deal on a yz80 pipe, which I think was one of the ones you recommended. I can't wait to install it. I'm hoping for an overall power increase as I'm not too concerned with top speed.