Air/oil-cooled internal combustion engine

An air/oil-cooled internal combustion engine including:

• cooling fins that are provided on circumferences of a cylinder block and a cylinder head;
• and
• a cooling passage that is provided in a combustion chamber upper wall covering a combustion chamber of said cylinder head and is used for cooling said combustion chamber upper wall with lubrication oil, wherein
• a temperature sensor configured to detect a temperature of said air/oil-cooled internal combustion engine by detecting a temperature of oil is provided to face a cooling oil outlet portion of said cooling passage,
• wherein said cooling passage in said combustion chamber upper wall of said cylinder head includes oil feed side inlet openings that communicate with an oil feed passage of said cylinder block, includes inside said combustion chamber upper wall oil passages that are led from said inlet openings and pass through a periphery of an ignition plug, and includes a communicating passage that couples said oil passages to each other at a position downstream of said inlet openings;
• and wherein said air/oil-cooled internal combustion engine includes cam chain chambers provided in the cylinder block and the cylinder head, and said cooling oil outlet portion of said cooling passage opens to the inside of the cam chain chamber of the cylinder head.