COOLING FIN STRUCTURE FOR VEHICLE-MOUNTED INTERNAL COMBUSTION ENGINE

摘要

An internal combustion engine 10 mounted on a motorcycle has a forward-tilted or substantially horizontal cylinder and is provided on its upper surface with a cooling fin structure 31 including cooling fins 30 extending in a direction in which the motorcycle advances. Reinforcing bulges 34 are formed integrally with the cooling fins 30 on the surfaces of the cooling fins 30 such that the reinforcing bulges 34 of each cooling fin 30 are separated from the adjacent cooling fins 30 and from the reinforcing bulges 34 of the adjacent cooling fins 30. The respective reinforcing bulges 34 of the adjacent ones of the cooling fins 30 are arranged alternately. The respective reinforcing bulges 34 of the adjacent cooling fins 30 do not overlap each other when seen in a direction along the length of the cooling fins 30. Bottom walls 35 continuously extending in the running direction of the motorcycle are formed between the adjacent ones of the cooling fins 30. Sand and mud can hardly accumulate in the cooling fin structure 31, which enables easy cleaning of the cooling fin structure. The cooling fin structure can prevent reduction of the cooling ability thereof.