INTERNAL COMBUSTION ENGINE AND STRADDLE-TYPE VEHICLE EQUIPPED WITH THE ENGINE

It is possible to detect knocking appropriately in a single-cylinder internal combustion engine in which a knock sensor is mounted to a part other than a cylinder block. A crankcase (11), a cylinder block (12), and a cylinder head (13) are connected by a bolt (60). A boss (40) for mounting a knock sensor (41) is formed on the crankcase (11). The center (40c) of the boss (40) is positioned on a side with respect to a cylinder axis (L1) in which the bolt (60) is provided, when viewed in an axial direction of the boss (40).