 The first two model years (XS-1 and XS-1B) were kick start only, with an electric starter added from the 1972 model year on.This had a compression release added to the front left exhaust tappet cover resulting in a square versus triangular cover found on the other exhaust and intake covers.Upon removal of the compression release mechanism in 1974 due to updated starter, the square cover at the left exhaust valve was continued.