A linking arm (36) conveying generally linear movement from a piston (30) into generally radial movement of a crankshaft (50) is disclosed. The linking arm includes a shaft (54) extending between a piston pin end (52) and a crankshaft pin end (50). The piston pin end (52) defines a piston pin bore (66). A piston pin bore surface (68) is defined by the piston pin bore (66), where the piston pin bore (66) includes a non-circular transverse profile (70) having at least two curved surfaces (72, 74) that each include a distinct radius, where the at least two curved surfaces are positioned in different locations around a periphery of the transverse profile (70).