Saddle-straddling type motor vehicle

A saddle-straddling type motor vehicle, comprising:

• a body frame situated from a front part to a rear part of said motor vehicle;
• and
• an air-cooled engine attached to said body frame,
• said body frame including
• a head pipe disposed approximately uprightly in the front part of said motor vehicle;
• and
• a main frame extending rearward and obliquely downward from said head pipe, and
• said air-cooled engine including
• a cylinder block forming a cylinder that reciprocatably accommodates a piston;
• a cylinder head forming a combustion chamber together with said cylinder block and having a primary passage communicating with said combustion chamber through an intake valve opening;
• an intake valve provided to open and close said intake valve opening;
• a fuel injection device having an injection nozzle that injects fuel;
• and
• a secondary passage that branches off from upstream of said primary passage and that guides air to a vicinity of said injection nozzle of said fuel injection device at least when said air-cooled engine is idling;
• said cylinder head being located in a front part under said main frame and said cylinder block being located in a rear part under said main frame such that a center axis of said cylinder extends approximately horizontally in a front-to-rear direction of said motor vehicle and so that said cylinder head is hit by a wind when said motor vehicle runs, and
• said fuel injection device being provided in said cylinder head so that said fuel injection device injects the fuel toward said intake valve opening from an injection passage in a side wall of said primary passage.