A reciprocating-piston engine, having • a cylinder block, • a crank chamber which is formed at least partially in the cylinder block, • a crankshaft which is composed of a magnetizable material and is arranged within the crank chamber so as to be rotatable about a geometric crankshaft axis, • at least one first connecting rod which is mounted rotatably in a first connecting-rod bearing of the crankshaft and which, during rotation of the crankshaft, performs a connecting-rod movement in a geometric connecting-rod movement space, • a first inner magnetic field unit (8a; 34), said first inner magnetic field unit being arranged on a first crank web, which is axially adjacent to the first connecting-rod bearing in relation to the crankshaft axis, of the crankshaft in such a way that the first inner magnetic field unit (8a; 34) points radially outward in relation to the crankshaft axis and, during rotation of the crankshaft, circulates around the crankshaft axis on a geometric first circular path which is axially adjacent to the connecting-rod movement space, and • a first outer magnetic field unit (11a; 37) which is arranged in static fashion in the crank chamber so as to be radially spaced apart from the first circular path, wherein the first inner magnetic field unit (8a; 34) and the first outer magnetic field unit (11a; 37) are arranged and configured such that, together, they form a first electromechanical converter, in particular an electric motor or an electrical generator, characterized in that • the first crank web has a first fastening surface on a side which points radially outward in relation to the crankshaft axis and which is situated opposite the first connecting-rod bearing, • a first balancing weight is fixed in positively locking fashion in a radial direction to the first fastening surface, • the first balancing weight is composed of a non-magnetizable material, and • the first inner magnetic field unit (8a; 34) is arranged on a side, which points radially outward in relation to the crankshaft axis, of the first balancing weight. • a cylinder block, • a crank chamber which is formed at least partially in the cylinder block, • a crankshaft which is composed of a magnetizable material and is arranged within the crank chamber so as to be rotatable about a geometric crankshaft axis, • at least one first connecting rod which is mounted rotatably in a first connecting-rod bearing of the crankshaft and which, during rotation of the crankshaft, performs a connecting-rod movement in a geometric connecting-rod movement space, • a first inner magnetic field unit (8a; 34), said first inner magnetic field unit being arranged on a first crank web, which is axially adjacent to the first connecting-rod bearing in relation to the crankshaft axis, of the crankshaft in such a way that the first inner magnetic field unit (8a; 34) points radially outward in relation to the crankshaft axis and, during rotation of the crankshaft, circulates around the crankshaft axis on a geometric first circular path which is axially adjacent to the connecting-rod movement space, and • a first outer magnetic field unit (11a; 37) which is arranged in static fashion in the crank chamber so as to be radially spaced apart from the first circular path, • the first crank web has a first fastening surface on a side which points radially outward in relation to the crankshaft axis and which is situated opposite the first connecting-rod bearing, • a first balancing weight is fixed in positively locking fashion in a radial direction to the first fastening surface, • the first balancing weight is composed of a non-magnetizable material, and • the first inner magnetic field unit (8a; 34) is arranged on a side, which points radially outward in relation to the crankshaft axis, of the first balancing weight.