An internal combustion engine comprising an internal combustion engine main body that includes a crankcase, a cylinder block provided on top of the crankcase, a cylinder head provided on top of the cylinder block, and a head cover provided on top of the cylinder head, wherein an upper and lower direction is along a vertical direction, a front and rear direction is perpendicular to the vertical direction, and a left and right direction is perpendicular to the vertical direction and the front and rear direction, wherein the internal combustion engine main body is attached to a main body frame such that a cylinder axis thereof is substantially parallel to the vertical direction and a crank axis extends in the left and right direction, wherein the internal combustion engine further comprises: a carburetor provided on a rear side of the cylinder head, the carburetor is provided with a carburetor body internally having an intake passage extending in the front and rear direction, a front end of the intake passage being connected to an intake port of the cylinder head and a rear end of the intake passage forming an air inlet port; and a fire-resistant cover member having a front wall provided on the rear side of the cylinder head and wall facing the air inlet port via a gap, the front wall having a plate shape having a major plane facing in the front and rear direction; wherein the cover member further includes a lower wall extending from a lower edge of the front wall of the cover member toward the carburetor, and having a cover member opening passed vertically through the lower wall, characterized in that the engine further comprises a breather tube having an inlet end connected to a crank chamber of the internal combustion engine main body, and an outlet end supported by the cover member at a position located between the front wall of the cover member and the carburetor. wherein an upper and lower direction is along a vertical direction, a front and rear direction is perpendicular to the vertical direction, and a left and right direction is perpendicular to the vertical direction and the front and rear direction, wherein the internal combustion engine main body is attached to a main body frame such that a cylinder axis thereof is substantially parallel to the vertical direction and a crank axis extends in the left and right direction, wherein the internal combustion engine further comprises: a carburetor provided on a rear side of the cylinder head, the carburetor is provided with a carburetor body internally having an intake passage extending in the front and rear direction, a front end of the intake passage being connected to an intake port of the cylinder head and a rear end of the intake passage forming an air inlet port; and a fire-resistant cover member having a front wall provided on the rear side of the cylinder head and wall facing the air inlet port via a gap, the front wall having a plate shape having a major plane facing in the front and rear direction; a carburetor provided on a rear side of the cylinder head, the carburetor is provided with a carburetor body internally having an intake passage extending in the front and rear direction, a front end of the intake passage being connected to an intake port of the cylinder head and a rear end of the intake passage forming an air inlet port; and a fire-resistant cover member having a front wall provided on the rear side of the cylinder head and wall facing the air inlet port via a gap, the front wall having a plate shape having a major plane facing in the front and rear direction; wherein the cover member further includes a lower wall extending from a lower edge of the front wall of the cover member toward the carburetor, and having a cover member opening passed vertically through the lower wall, characterized in that the engine further comprises a breather tube having an inlet end connected to a crank chamber of the internal combustion engine main body, and an outlet end supported by the cover member at a position located between the front wall of the cover member and the carburetor.