Abstract: A crankshaft drive for an internal-combustion engine includes a crankshaft, a connecting rod assembly coupled to the crankshaft, and a balancing shaft arranged parallel to the crankshaft and at a distance r from the crankshaft. A balancing weight extends from the balancing shaft for balancing mass forces caused by the rotation of the crankshaft. A recess is formed in the balancing weight, so that during rotation of the balancing shaft, the balancing weight does not interfere with the rotating crankshaft and connecting rod assembly. The inclusion of the recess allows the distance r between the crankshaft and the balancing shaft to be reduced. Preferably, a rib is formed on one side of the balancing shaft to strengthen the balancing shaft.

Abstract: A crankshaft drive for an internal-combustion engine includes a crankshaft, a connecting rod assembly coupled to the crankshaft, and a balancing shaft arranged parallel to the crankshaft and at a distance r from the crankshaft. A balancing weight extends from the balancing shaft for balancing mass forces caused by the rotation of the crankshaft. A recess is formed in the balancing weight, so that during rotation of the balancing shaft, the balancing weight does not interfere with the rotating crankshaft and connecting rod assembly. The inclusion of the recess allows the distance r between the crankshaft and the balancing shaft to be reduced. Preferably, a rib is formed on one side of the balancing shaft to strengthen the balancing shaft.

Abstract: A motorcycle engine includes a crankshaft rotating in response to the reciprocation of pistons in cylinder bores. The inertial effects of the reciprocating pistons cause vibrations in the engine. A pair of balancer shafts are provided on opposite sides of the crankshaft, and are driven by the crankshaft through a drive member, such as a chain or belt. The balancer shafts are supported for rotation by bearings in the left side of the engine's crankcase, and by bearings in bearing housings that are mounted to the left side of the engine's crankcase. Thus, the balancer shafts are substantially only supported for rotation by the left side of the crankcase.