Abstract: A power transmission system transmits rotative power from a driver pulley to a driven pulley through a toothed belt. The tooth tips (27b) and/or tooth bottoms (27c) of teeth of at least the driven pulley (10) lie in a plane including a central axis l.sub.2 of rotation of the driven pulley and are inclined with respect to the central axis l.sub.2. When the toothed belt (14) is operated to transmit the rotative power, the position where teeth of the pulley (10) and teeth of the toothed belt (14) start meshing with each other is progressively displaced, thus lowering the level of impact sounds produced when the teeth mesh with each other.

Abstract: An engine balancer driving arrangement is disclosed having a plurality of sprockets or belt pulleys mounted, respectively, on a driving shaft of an oil pump or the like, on the crankshaft, and on the shafts of said balancers and a single endless timing chain or corrugated belt engaged with all of said sprockets or belt pulleys. The two sprockets or belt pulleys, which are mounted on the balancer shafts, are brought into engagement with the inner and outer periphery of said timing chain, respectively. The oil pump or other auxiliary mechanism is disposed within a dead space which is formed by the cam shaft driving mechanism between the front wall of the engine and said balancer driving mechanism thereby reducing the overall length of the engine.

Abstract: Balancer shafts are provided on the right and left of the crank shaft of an engine and so as to be driven thereby. Each balancer shaft has a balance weight divided into two portions, one on either side of a bearing supporting the balancer shaft. This construction protects the bearings from undesirable wear.

Abstract: Means for actuating a balancer of an engine including a crankshaft, pistons and connecting rods, comprising a pair of balancer shafts located opposite sides of the crankshaft and actuated thereby. One of the balancer shafts is formed to serve for a rotatable shaft of a subsidiary device of the engine, such as an oil pump, an air pump, a dynamo or a water pump.