I was so thrilled to find a cheap muffler on Ebay for my "mostly 1972" ATC90. I'm not sure which parts are original on this thing, which is why I say mostly. Anyway, the seller said this muffler was from a 1972, but it's got a spark arrestor on the end and doesn't fit. They didn't have spark arrestors in '72, did they?
Here's some pics of the two mufflers. I'm open to suggestions.