This is a scene from the 1961 Tecate (Mexico) 100 mile endurance race. Design features that were developed for races like this formed the basis of what eventually evolved into today's "Enduro" kart. The kart caught in this action shot is pretty much the standard sprint kart of its day (except for what appears to be a mega gas tank behind the seat). Check out the special enduro Caretta kart from this same race to see the start of some real enduro design evolution.