An engine, comprising: a cylinder; a crankcase connected to the cylinder; a crankshaft; a connecting rod; a piston configured to make reciprocating motion in the cylinder; the crankshaft being connected via the connecting rod to the piston, and being configured to rotate about a crank axis in conjunction with the reciprocating motion of the piston, at least a part of the crankshaft being arranged in the crankcase; an oil pan provided in the crankcase; a reservoir part provided in the crankcase and storing oil; a scavenge pump that feeds the oil from the oil pan to the reservoir part; and a balance shaft arranged between at least the part of the reservoir part and the crankshaft and being configured to rotate in conjunction with the crankshaft, characterized in that in an offset direction (Do) orthogonal to each of an axis (Lc) of the cylinder and the crank axis, the crank axis is located on one side of the axis (Lc) of the cylinder, at least a part of the reservoir part is located on the other side of the axis (Lc) of the cylinder in the offset direction (Do) and overlaps the crankshaft as viewed from the offset direction (Do), at least the part of the reservoir part includes a first reservoir chamber and a second reservoir chamber arranged in an axis direction of the balance shaft and oil is stored in the interior of each of the first reservoir chamber and the second reservoir chamber, a weight of the balance shaft is located between both ends of the second reservoir chamber in the axis direction of the balance shaft, the first reservoir chamber includes a projecting part projecting toward the balance shaft further than the second reservoir chamber in a normal direction normal to the axis direction of the balance shaft, and at least a part of the projecting part overlaps a rotational locus of the weight of the balance shaft as viewed from the axis direction of the balance shaft. a cylinder; a crankcase connected to the cylinder; a crankshaft; a connecting rod; a piston configured to make reciprocating motion in the cylinder; the crankshaft being connected via the connecting rod to the piston, and being configured to rotate about a crank axis in conjunction with the reciprocating motion of the piston, at least a part of the crankshaft being arranged in the crankcase; an oil pan provided in the crankcase; a reservoir part provided in the crankcase and storing oil; a scavenge pump that feeds the oil from the oil pan to the reservoir part; and a balance shaft arranged between at least the part of the reservoir part and the crankshaft and being configured to rotate in conjunction with the crankshaft, characterized in that in an offset direction (Do) orthogonal to each of an axis (Lc) of the cylinder and the crank axis, the crank axis is located on one side of the axis (Lc) of the cylinder, at least a part of the reservoir part is located on the other side of the axis (Lc) of the cylinder in the offset direction (Do) and overlaps the crankshaft as viewed from the offset direction (Do), at least the part of the reservoir part includes a first reservoir chamber and a second reservoir chamber arranged in an axis direction of the balance shaft and oil is stored in the interior of each of the first reservoir chamber and the second reservoir chamber, a weight of the balance shaft is located between both ends of the second reservoir chamber in the axis direction of the balance shaft, the first reservoir chamber includes a projecting part projecting toward the balance shaft further than the second reservoir chamber in a normal direction normal to the axis direction of the balance shaft, and at least a part of the projecting part overlaps a rotational locus of the weight of the balance shaft as viewed from the axis direction of the balance shaft.