The Two-Stroke Engine Cycle: Part One

Each cycle of any engine begins at the spark plug. Two-stroke engines derive their power from the fact that the spark plug fires once every rotation, as opposed to every other. When the spark plug fires, the mixture of fuel and air in the cylinder ignites to drive down the piston. As the piston moves downward, it compresses the mixture of air and fuel into the crankcase. The the piston creates pressure in the cylinder, pushing the gases out of the exhaust port.
 
The intake port is then covered as the piston reaches the bottom of the stroke. Because the mixture is pressurized in the crankcasae, it rushes into the cylinder. This displaces the excess gas and fills the cylinder with a new supply of fuel and Yamaha 2M oil. Now that this phase of the cycle is complete, tomorrow we’ll have the riveting conclusion: the compression stroke!