A few pictures of John Wayne on motorcycles.  The SL350 K0 in the first picture is obviously a prop bike as you can see the tubes in back of the front wheel and behind the rear seat.  These were used to secure the bike upright on a trailer so that it would appear he was riding.  It actually looks like he is using the bike to run around under its' own power.   I would suppose the picture of him on the mini-bike is one he used to run around the set location while filming a movie.