New guy here. This is a great thread. Here's a pic of me at the DC moto show a couple years ago with a pristine 78 XR75, which looks just like the one I had way back when (mine may have been less pristine ;) ).
The XR75 actually wasn't my first though. The first bike I had was a minibike with really fat tires. I remember taking it into a plowed field and riding across the grain kind of like whoops. With no suspension and the return cable for the throttle broken it was quite exciting if your right hand came off the bar. ;) I know there's a pic of me somewhere sitting on that thing in the family room on Christmas in 78 or so.