| 摘要 |
PURPOSE:To unlimitedly increase the opening areas of intake and exhaust ports, by forming two intake ports in one side section of a combustion chamber forming surface, symmetrically with respect to the line connecting between the center of the opening section of the exhaust port and the center of the engine cylinder. CONSTITUTION:A ceiling surface 22 of a combustion chamber 7 which is the lower surface of a cylinder head 5 is formed in a roof-like shape with first and second inclined surfaces 221, 222 having their border line which is a ridge line (a). Two intake port opening sections 23, 23 are formed in the first inclined surface 221, and one exhaust port opening section 24 and two plug fitting hole opening sections 25, 25 are formed in the second inclined surfaces 222. In this arrangement, the exhaust port opening section 24 is positioned at its center O1 on the line (b) passing through the center O2 of the combustion chamber 7 and orthogonal to the ridge line (a) while the two intake port opening sections 23, 23 are positioned substantially symmetrical with respect to the line (b), thereby it is possible to increase the opening area of each opening section at most. |
