Working Principle of 2-stroke engine

• The whole process i.e. Suction, compression, power and exhaust is completed in two strokes of piston and one complete revolution of crankshaft.
• There is no valve.
• Gas movement takes place through holes called ports of the cylinder.
• The crankcase is gas tight in which the crankshaft rotates.

A) First stroke (Suction+ Compression)

• Piston moves up the cylinder and covers two ports i.e. exhaust and transport port.
• This traps a charge of fresh mixture in the cylinder and further upward movement of piston compresses this charge.
• Further movement of piston uncovers suction port and more fresh mixture is drawn into the crankcase.
• Just before the end of this stroke, the mixture in the cylinder is ignited.

B) Second stroke (Power+ Exhaust)

• The burning of gases increases pressure in cylinder and forces the piston to move down the cylinder.
• When piston moves down, it covers and closes the suction port, trapping the mixture drawn into the crankcase.
• Further downward movement of piston uncovers first the exhaust port and then the transfer port.
• This allows the burnt gases to flow out through exhaust port.
• The fresh mixture under pressure in crankcase is then transferred into the cylinder through transfer port during this stroke.