Gonna have to say from the 60's. My Grandfather had one that he built in the mid 50's and boy, what a piece of equipment. His had a Cushman motor scooter clutch and a jack shaft, a steering quickener, the seat was a metal trash can padded and covered w/ vinyl. Had no hoop above the head and was alum body. Probably weighed 200 lbs... brazed together out of what looked like conduit. It used a 2hp Lawson motor off a reel type mower.It had a v-belt pulley w/ apiece of v-belt as a brake. Everything was home made.He was a machinist and I was impressed w/ the engine mods. The piston skirts were drilled to lighten them, matching weight removed from crank shaft,cam was welded on and reground, head was milled and had a very thin copper head gasket a Tillotson side draft carb, also had a Carter model N carb in boxes of parts.Really neat piece, Thanks for sharing. Greg