muffler remove

Seems the 391 gets the cold shoulder a lot since it’s just a home owner saw. But I did a muffler mod, my way and did not like it, so I was looking for a replacement. Found one one ebay for about $45, nah.... So I started to dig through IPL’s on the 311 and 362 but I stopped short and thought I...

I picked up a Jonsered 670 champ. Seems to have poor compression. I dont plan to repair or rebuilt it myself but I'd like to get familiar with it and what's wrong before sending it in to my local guy. Novice curiousity. I've removed the two longer Allen key bolts that pass through the muffler...