I designed and fabricated this expansion chamber exhaust for a 1965 Suzuki K15 (80cc 2-stroke) motorcycle.
I hand-cut and hand-formed it in my garage out of 26ga (0.45mm) mild steel. I used a TIG welder to combine the ~20 sections of the pipe.
It worked great, and sounded awesome. Sadly, I sold the bike before moving to Colorado.