Intake air heating device for internal combustion engine for motorcycles

In an internal combustion engine for a motorcycle wherein the engine is mounted on a motorcycle frame, the engine having an intake port and an exhaust port opening at its rear and front sides respectively, in the traveling direction of the motorcycle, the engine also having an air cleaner connected to a carburetor, which is in turn connected to said intake port, and the exhaust port is connected to an exhaust pipe leading to an exhaust muffler which is positioned rearward of the frame, said exhaust pipe having a part which extends downwardly in front of the engine and then along the side of the engine, an intake air heater, comprising:

• an air heater means for heating air before entering the intake port, said air heater means having an air heating chamber, disposed around at least part of said exhaust pipe, for heating intake air taken from the external atmosphere through an opening which is provided in the air heater means;
• and
• a heated air conduit extending in the longitudinal direction of the motorcycle and passing to the side of the engine cylinder within the transverse breadth of the engine for connection at one end thereof to the air heating chamber at a portion thereof located within the transverse breadth of the engine and at the other end to one side of the air cleaner.