An aluminium 2-stroke engine cylinder and the crank case assembly is provided, in which a cylinder flange rests in sealing manner over its entire area upon a corresponding counter-surface of the crank case and a deformable packing lies between the sealing surfaces and in which the flange is tightened to the crank case by means of screws. The mutually opposite sealing surfaces of flange and crank case are slightly inclined in relation to one another in such a way that the distance between the sealing surfaces is greater radially inwards than radially outwards.
