Gudgeon pins on new pistons were an interference fit and were only supposed to rotate in the small end bush. Usually, through lack of adequate lubrication, the gudgeon pin would partially seize in the small end bush and start to rotate in the piston causing wear in the gudgeon pin holes. In order to reclaim the piston and carry on using it, the pistons were bushed. It is possible to get oversize pins but it is better to try to keep every thing as standard as possible. Also the original gudgeon pins would have had brass pads on the ends of the pins and would not have been retained in the pistons by circlips
Dave
