Left crankshaft box body structure of horizontal balance shaft engine

The utility model discloses a left crankshaft box body structure of a horizontal balance shaft engine. A balance shaft installation hole (10) is arranged in a quadrangle enclosed by a crankshaft central hole (1), a main shaft central hole (2), a second box body hanging hole (6) and a starter motor central hole (4). A first starter motor screw fixing hole (7) is arranged in the left side of the starter motor central hole (4), the second starter motor screw fixing hole (8) is arranged in the lower right corner of the starter motor central hole (4), and the third starter motor screw fixing hole (9) is arranged in the upper right corner of the starter motor central hole (4). On the premise that the whole crankshaft box structure of a common horizontal balance shaft engine in the prior art is not changed, quadrangular space is enclosed by cleverly using the crankshaft central hole, the main shaft central hole, the second box body hanging hole and the starter motor central hole. Besides, the position of the first s