| 摘要 |
The inlet port in the crank case is provided with an inlet valve. Exhaust is via a number of exhaust ports arranged around the circumference of the cylinder wall. The overflow consists of a number of longitudinal ducts spaced around the circumference of the cylinder wall. The arrangement of ports and ducts may be symmetrical, and ports may alternate with ducts. The distance from the cylinder head to the highest point of the ducts is pref. greater than that to the top of the ports. The relative position of ports and ducts is preferably such that, on its downward stroke, the piston opens at least half the cross-sectional port area before reaching the highest point of the ducts. The inlet valve may be a rotary disc valve coupled to the crank shaft. |
