Patent ID: 8720403

Claim:
An engine comprising a crankshaft and two balancer shafts, wherein: the two balancer shafts are arranged in such a manner that the axes of the two balancer shafts have a phase angle difference of substantially 180 degrees between the balancer shafts around the crankshaft axis, a pair of journal portions is formed on opposite ends of each of the balancer shafts in the axial direction of the balancer shaft, the journal portions being rotatably supported by a crankcase, a first stage balance weight is formed between the journal portions, the first stage balance weight being eccentrically arranged relative to an axis of the journal portions and having a recess portion on the opposite side of an eccentricity direction of the first stage balance weight, a second stage balance weight is formed on a substantially center part of the first stage balance weight in the axial direction of the first stage balance weight, the second stage balance weight further projects outward from the first stage balance weight in the radial direction, and the second stage balance weight is positioned between crank arms of the crankshaft when seen in a direction orthogonal to the axial direction of the balancer shaft, and one part of the second stage balance weight can pass between the crank arms.