Abstract: An internal combustion engine capable of reducing an amount of dust taken from an outside air intake opening, with a simple configuration. The internal combustion engine includes a crankshaft, a cooling air intake device that houses a cooling fan coupled to the crankshaft and that includes a cooling air intake port, and an air cleaner device that feeds outside air to an air suction port to a cylinder, and the air cleaner device includes an outside air intake opening that opens toward the cooling air intake port.

Abstract: A breather apparatus is provided in a cylinder head having an intake camshaft and an exhaust camshaft that drive an intake valve and an exhaust valve, respectively. The breather apparatus includes, spaces separated from each other by partition walls and in communication with each other through an opening formed in the partition walls, the spaces having a blow-by gas flowing from a crankcase side passing sequentially therethrough. The spaces include a first space and a second space. The first space is formed in a region between the intake valve and the exhaust valve in the cylinder head. The second space is provided across the first space from a crankcase side, separated from the first space by a partition wall disposed substantially along a plane including shaft centers of the intake camshaft and the exhaust camshaft, and receives the blow-by gas flowing from the first space.