Honda C90

The blue one... having thought about this on-and-off all week, I can only assume that the wear on the hole in the frame through which the bolt passes is the result of the nut being loose at some point in its past, possibly made worse by the chain being too tight? However on these bikes the front end of the swing arm is rubber bushed, all the boilt has to do is hold it all together (including the exhaust pipe bracket). It doesnt act as a pivot, the rotational movement of the swing arm is allowed for the the flex in the rubber bushings.

Going back together... come to think of it this would explain why the rear wheel has always been mis-alligned in the frame?