J.S.@SMS
Road Hazard
Info is scarce but I guesstimate about the late 1980's to mid 1990's. After that they radically changed the designs [in the early 2000s I think], mandatory "roll cages" (or brush guards), seat belts, etc., and many of the manufacturers completely enclosed the axles with a plastic guard or casing. The reason being there were some accidents wherein riders were injured when loose clothing and long hair came into contact with a spinning shaft and got tangled.
My Ken-Bar Streaker literrally fits each one of those descriptions. It has brush bars, seat belts, plastic guards on the axle (over metal spacers which turned out to be a total PITA) And I have a different kart that was recalled for that reason.