Johnson Evinrude Outboard Motors 1956-1970 1.5-40hp repair manual., Page 43Get this manual
INTRODUCTION is ignited; and the power stroke beginsThe reed valve was open because as the piston moved upward, the crankcase volume increased, which reduced the crankcase pressure to less than the outside atmosphereAs the piston moves downward on the power stroke, the combustion chamber is filled with burning gasesAs the exhaust port is uncovered, the gases, which are under great pressure, escape rapidly through the exhaust portsThe piston continues its downward movementPressure within the crankcase increases, closing the reed valves against their seatsThe crankcase then becomes sealed chamberThe-fuel mixture is compressed ready for delivery the combustion chamberAs the piston continues to move downward the intake port is uncoveredFresh fuel rushes through the intake port into the combustion chamber striking the top of the piston where it is deflected along the cylinder wallThe valve remains closed until the piston moves upward againWhen the piston begins to move upward on the compression stroke, the reed valve opens because the crankcase volume has been increased, reducing crankcase pressure to less than the outside atmosphereThe int.ake and exhaust ports are closed and the fresh fuel charge is compressed inside the combustion chamber 3-3