External combustion engine comprising: - a first cylinder and a second cylinder, disposed angularly offset in a fixed position with respect to each other, in which a first piston and a second piston are able to slide respectively, said first and second cylinder being fluidically connected with respect to each other for the passage of a heat-carrying fluid suitable to determine the cyclical movement of said first piston and said second piston; - a drive shaft rotating around an axis of rotation, and with which crank means are solidly associated, said crank means being provided with at least a first pin and at least a second pin having pivoting axes (J, K) parallel to each other, and also disposed distanced radially from said axis of rotation; and - first (22, 23) and second kinematic connection means suitable to connect respectively said first pin and said second pin to said first piston and respectively said second piston so as to provide, together with said crank means, for the rotation of said drive shaft, wherein said first pin and said second pin are disposed with the respective pivoting axes (J, K) angularly offset so that said first pin and said second pin are angled by a desired angular amplitude equal to a first acute angle (β) with respect to said axis of rotation, characterized in that said first pin and said second pin are distanced radially by a first distance and by a second distance with respect to said axis of rotation, said first distance and said second distance being different from each other so as to determine a differentiated travel of the first piston with respect to that of the second piston. - a first cylinder and a second cylinder, disposed angularly offset in a fixed position with respect to each other, in which a first piston and a second piston are able to slide respectively, said first and second cylinder being fluidically connected with respect to each other for the passage of a heat-carrying fluid suitable to determine the cyclical movement of said first piston and said second piston; - a drive shaft rotating around an axis of rotation, and with which crank means are solidly associated, said crank means being provided with at least a first pin and at least a second pin having pivoting axes (J, K) parallel to each other, and also disposed distanced radially from said axis of rotation; and - first (22, 23) and second kinematic connection means suitable to connect respectively said first pin and said second pin to said first piston and respectively said second piston so as to provide, together with said crank means, for the rotation of said drive shaft, wherein said first pin and said second pin are disposed with the respective pivoting axes (J, K) angularly offset so that said first pin and said second pin are angled by a desired angular amplitude equal to a first acute angle (β) with respect to said axis of rotation, characterized in that said first pin and said second pin are distanced radially by a first distance and by a second distance with respect to said axis of rotation, said first distance and said second distance being different from each other so as to determine a differentiated travel of the first piston with respect to that of the second piston.