| 摘要 |
PURPOSE:To improve combustion efficiency, by a method wherein two intake ports are formed in the one side of a cylinder head around a surface including the central line of a combustion chamber, and a third intake port and an exhaust port are formed in the other side. CONSTITUTION:First and second parts 20 and 21 are formed in the one side of a cylinder head 2 around a surface including the central line of a crank shaft and the central line of a combustion chamber, and are opened and closed by first and second valves 8 and 9. A third intake port 22 and an exhaust port 23 are formed in the other side of the cylinder head 2, and are opened and closed by a third intake valve 10 and an exhaust valve 11, respectively. The first and second intake ports 20 and 21, the third intake ports 22 and the exhaust ports 23 of adjoining cylinders are collected to each other in the cylinder head 2. The first intake valve 8 is operated normally during a time between a high speed to a low speed, the second intake valve 9 is operated during a time between a middle speed and a high speed, and the third intake valve 10 is operated during high speed running.
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