The invention relates to a two-stroke diesel engine with a quadrangular piston in which the intake and exhaust cycle with secondary expansion is performed by in each case two opposing oscillating pistons moved by a crank shaft via connecting rods. The connecting-rod pairs which move the oscillating pistons are configured in such a way that they are supported at the sides on the flat surfaces of the engine casing and slide upon them. The simple, hollow-cast crank shaft is fitted with separately encased eccentric masses revolving outside the engine casing for the purpose of balancing the oscillating masses.
