Abstract: A balance system for an internal combustion engine or the like includes a counterbalance weight pivotally mounted to the crankcase and driven in a reciprocating manner by a link assembly connecting the weight to an eccentric on the crankshaft. The pivoting weight not only counterbalances the piston acceleration and deceleration forces but also cancels the torsional forces created by the weight as it pivotally moves through an arc in response to piston movement. This is accomplished by locating the center of gravity of the balance weight between the piston bore centerline and the stationary pivot of the balance weight itself. This location for the center of gravity causes a torque to be generated by a force couple created by the piston inertial force vector, the balance weight interial force vector, and the distance between them. This torque counteracts the torque generated by angular acceleration of the balance weight itself, to thereby substantially eliminate all torsional vibrations.