| 摘要 |
A cylinder head for a twin overhead valve air-cooled internal combustion engine comprising an upper plate and a lower plate so interconnected by valve ports, ribs and walls to define passages through which cooling air can flow. The ribs and walls extend from air inlet places to the vicinity of an injection nozzle and said valve ports substantially parallel to the cylinder axis and obliquely to a plane of symmetry of the cylinder head passing parallel to said cylinder axis through a central cooling air duct in the cylinder head. The valve ports extend transversely to the said plane of symmetry substantially over the entire width of the cylinder head. Cooling air guide walls surround the cylinder head on sides thereof adjacent said air inlet places and extend at least approximately as far as said valve ports. These guide walls are arranged so that cooling air flows partly over the sides of the valve ports which are nearest to said ribs and walls but otherwise is forced to flow through said central cooling air duct.
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