Abstract: An internal combustion engine includes a crankshaft and a balancer shaft. The shafts are rotationally linked to one another, and the crankshaft is linked to a piston. The shafts carry weights to minimize the vibrations caused by the reciprocating motion of the piston. A reinforcing member has two enclosing portions, one for a bearing of each of the shafts, and integrally joins both of said enclosing portions. The reinforcing member is cast into the crankcase wall. Its material is stronger than the material of which the crankcase wall is made. Cracking and wearing of the crankcase wall, especially in the region between the two shafts, is reduced or eliminated, and the wall can be made thinner, and more reliably without cavities.