Abstract: In an internal combustion engine a piston reciprocates within a cylinder such that outward power strokes alternate with outward induction strokes. A power transfer lever pivotally mounted intermediate its ends has one end being connected to a throw of a crankshaft through a crank rod. Reciprocation of the piston causes rotation of the crankshaft by transfer of forces through the transfer lever and crank rod. The pivotal mount of the power transfer lever is supported by eccentric means rotatably driven through gear train at half cranks haft speed whereby the effective pivot point of the power transfer lever oscillates laterally of the power transfer lever causing successive outward strokes of the piston to be alternately long and short strokes. The engine may therefore be arranged so that the power stroke is shorter than the induction stroke.