Two-stroke engine

A two-stroke engine comprising:

• a cylinder provided with an approximately cylindrical shape;
• and
• a piston that can reciprocate between a top dead center position and a bottom dead center position in the cylinder,
• the cylinder including:
• an exhaust port configured to be able to discharge exhaust gas;
• and
• a scavenging port configured to be able to deliver scavenging air containing fuel and air in an anti-discharge direction approximately opposite to a discharge direction of the exhaust gas, wherein:
• the piston has a top surface, part of the top surface being concave and comprising a piston concave portion;
• an entire surface of the piston concave portion having an approximately spherical shape;
• and
• a slope of the piston concave portion extending from an outer circumferential edge of the piston concave portion in the discharge direction, to a deepest portion, is steeper than a slope of the piston concave portion extending from an outer circumferential edge of the piston concave portion, in the anti-discharge direction, to the deepest portion;
• the piston concave portion has a width dimension extending in the discharge direction and in the anti-discharge direction and orthogonal to a bore center line of the cylinder, and
• a half or larger portion of the width dimension is on the exhaust port side with respect to the bore center line.