In this engine, the working cycle is completed in
two strokes of the piston or one revolution of
the crank shaft. It will be easier to describe the
cycle beginning at the point when the piston has
reached to TDC completing the compression
stroke, the spark is produced by spark plug as
the piston reaches TDC but here a bulb is
provided to show the spark timing.(the bulb will
glow at the time of sparking) When the piston
uncovers the exhaust port during the downward
stroke, the burnt gasses leave the cylinder
through the exhaust port. A little later, the piston
uncovers (opens) the transfer port in this
position, the crank-case is directly connected to
the cylinder through port. During the downward
stroke of the piston, the charge in the crankcase
is compressed by the underside of the piston at
this position; the compressed charge (fuel &air)
is transferred through the transfer port to the
upper part of the cylinder. The exhaust gases are
swept out with the help of fresh charge.

In this engine, the working cycle is completed in
two strokes of the piston or one revolution of
the crank shaft. It will be easier to describe the
cycle beginning at the point when the piston has
reached to TDC completing the compression
stroke, the spark is produced by spark plug as
the piston reaches TDC but here a bulb is
provided to show the spark timing.(the bulb will
glow at the time of sparking) When the piston
uncovers the exhaust port during the downward
stroke, the burnt gasses leave the cylinder
through the exhaust port. A little later, the piston
uncovers (opens) the transfer port in this
position, the crank-case is directly connected to
the cylinder through port. During the downward
stroke of the piston, the charge in the crankcase
is compressed by the underside of the piston at
this position; the compressed charge (fuel &air)
is transferred through the transfer port to the
upper part of the cylinder. The exhaust gases are
swept out with the help of fresh charge.