In 1970 I was trevelling with some friends from Sweden to the Isle of Man. In the group was a new CB750 delivered in the autumn 1969 in Sweden. At our way back to Sweden the drive chain snapped in a bump a made a hole in the engine block. The chain was obviousily too tensed. On that model there was no protection for snapping chains in front of the small sprocket on the outgoing shaft from the gearbox. Later there were a cover to protect the engine block from such disasters. Was the CB750 in our group one of the very first models, please? The hole was later repaired with some stuff called Belzona!