Steve - you will always be a kid to some of us...
Amazing the things you never knew existed, and I was around in the 80's, and the 70's, and the 60's, and half of the 50's...
...and I'm still around since then too.
Back in those early 70's we (mostly my dad) used the horizontal shaft engine and over center clutch off a Jacobson two stroke powered reel type mower on a mini-bike that I used to tear around on. It was not a rear user friendly design, lever type throttle on the handlebars and reach down behind you to engage the clutch, but we had a lot of fun.
Mark