An angular interval between a piston top dead center of one of two cylinders of an engine and a piston top dead center of the other one of the two cylinders is not a quotient of 360.degree. CA divided by an integer number. A timing rotor is rotated synchronously with a crankshaft of the engine and includes a plurality of teeth that are arranged at equal intervals, each of which is set as a predetermined quotient of the angular interval divided by a corresponding integer number.
