Abstract: There is provided a secondary air introduction device configured to introduce air into an exhaust port provided in a cylinder head of an engine by using a negative pressure in the exhaust port. A back-flow restriction member is provided between a reed valve and the exhaust port in an air introduction passage, and includes a plate part intersecting with an extension direction of the air introduction passage. The plate part has an air passing region in which the air flowing through the air introduction passage from an air intake unit toward the exhaust port is enabled to pass therethrough and a back-flow cutoff region in which exhaust air, which flows in a direction of directly colliding with at least a valve body of the reed valve, of exhaust air flowing back through the air introduction passage from the exhaust port is cut off.

Abstract: There is provided a secondary air introduction device configured to introduce air into an exhaust port provided in a cylinder head of an engine by using a negative pressure in the exhaust port. A back-flow restriction member is provided between a reed valve and the exhaust port in an air introduction passage, and includes a plate part intersecting with an extension direction of the air introduction passage. The plate part has an air passing region in which the air flowing through the air introduction passage from an air intake unit toward the exhaust port is enabled to pass therethrough and a back-flow cutoff region in which exhaust air, which flows in a direction of directly colliding with at least a valve body of the reed valve, of exhaust air flowing back through the air introduction passage from the exhaust port is cut off.