ENGINE

An engine (40) to be mounted on a straddle-type vehicle (1). The engine (40) includes a cylinder (42) and a cylinder head (43) stacked on an upper portion of a crank case (41), an exhaust pipe (70) extending from the cylinder head (43) and passing through a lateral side of the cylinder (42), an exhaust gas sensor (86) attached to the exhaust pipe (70), on the lateral side of the cylinder (42), and a radiator (51) positioned in front of the cylinder head (43). The exhaust gas sensor (86) is covered by the radiator (51) from a front side.