Portable power tool having internal combustion engine

摘要

A portable power tool includes an internal combustion engine that includes a crankshaft in which a load applied thereto is unevenly distributed along the axis of the crankshaft with respect to the axis of the reciprocating movement of a piston. The portable power tool also includes operational members that are driven by the internal combustion engine, a rotational body fixed to an end of the crankshaft to which a smaller component of the load is applied, and a balancing weight provided on the rotational body for absorbing vibrations generated by the reciprocating movement of the piston. The centroid of the balancing weight is disposed at an angular position from 140 degrees to 180 degrees with respect to the axis of the reciprocating movement of the piston in a rotational direction of the rotational body, when the piston is positioned at a top dead center.