1. Suctionand compression stroke
吸气和压缩冲程

When the pistonmoves from bottom dead centre to top dead centre, a fuel-air mixture, suppliedby the carburetor, is drawn into the crankcase. At the same timethe fuel-air mixture above the piston is being compressed. This mixture hadearlier on passed from the crankcase into the cylinder. Immediately before this mixture is ignited, the exhaust port is closed by the poiston.
当活塞从下死点运动到上死点，化油器提供的油气混合物，被吸进曲轴箱。与此同时，活塞上面的油气混合物被压缩。这些混合物之前由曲轴箱运动到气缸。排气口一被活塞关闭，混合物马上被点燃。

2.Power and evhaust stroke
做功和排气冲程

Followingignition, the expanding gases force the piston downwards. On its downwardmovement the piston first uncovers the exhaust port. Before reaching its bottomdead centre, the upper edge of the piston uncovers the transfer passage,through which the mixture, precompressedin the crankcase, passes into the combustion chamber. The scavenging effect ofthe-air mixture entering from the crankcase assists in flushing out thecombustion gases from the cylinder.
点燃后，膨胀的气体推动活塞向下运动。在它向下运动的过程中，活塞第一次没有覆盖排气孔。在到达下死点之前，活塞的上沿没有覆盖换气通道，混合气通过它进入，在曲轴箱中的预压下，进入燃烧室。
混合气的扫气过程就是，从曲轴箱进入，帮助排出活塞中燃烧的气体。

Piston活塞 Piston pin活塞销 Spark plug火花塞 Cylinder汽缸
Crankshaft曲轴 Crankcase曲轴箱 Crank pin曲轴销
Con rod连杆 Oscillating weight摆轮 Carburetor汽化器
Suction port进气孔 Transfer port传送孔 Exhaust port排气孔
Inpuls line脉冲管路