Abstract: A cooling structure of an internal combustion engine includes a thermostat provided to switch circulation between a radiator passage and a bypass passage in an engine body, to thereby enable acceleration of early warming up via the bypass passage without impairing the external appearance or increasing the size of the internal combustion engine. The cooling structure also includes an in-cylinder-block fluid passage partitioned up and down in an axial direction of a cylinder axis into an in-cylinder-block upper fluid passage and an in-cylinder-block lower fluid passage by a partition wall. The bypass passage is partially composed of the in-cylinder-bock lower fluid passage.

Abstract: A cooling structure of an internal combustion engine includes a thermostat provided to switch circulation between a radiator passage and a bypass passage in an engine body, to thereby enable acceleration of early warming up via the bypass passage without impairing the external appearance or increasing the size of the internal combustion engine. The cooling structure also includes an in-cylinder-block fluid passage partitioned up and down in an axial direction of a cylinder axis into an in-cylinder-block upper fluid passage and an in-cylinder-block lower fluid passage by a partition wall. The bypass passage is partially composed of the in-cylinder-bock lower fluid passage.

Abstract: A cover structure for an internal combustion engine covers and protects a coolant pipe of a cooling system component on an internal combustion engine, even when the internal combustion engine only has a short distance provided between a crankshaft and an output shaft. The cover structure includes an outer cover disposed outside an inner cover, thereby defining a space between the first and outer covers. Coolant conduits, which are in fluid communication with a cooling system component, are constructed and arranged to pass through the space between the first and outer covers.

Abstract: A cover structure for an internal combustion engine covers and protects a coolant pipe of a cooling system component on an internal combustion engine, even when the internal combustion engine only has a short distance provided between a crankshaft and an output shaft. The cover structure includes an outer cover disposed outside an inner cover, thereby defining a space between the first and outer covers. Coolant conduits, which are in fluid communication with a cooling system component, are constructed and arranged to pass through the space between the first and outer covers.