suck, squeeze, burn and blow

How an engine works … “The Basics”
(referenced from BW Cycle)

To start any engine, Two or Four stroke, you must have 3 things.
One– A burnable mixture of something. It can be
gasoline,starting fluid, carb cleaner, shoot, it could
be spray deodorant ! But it mustbe able to burn.
Two– It must be compressed, that is under compression
by thepiston.
Three– there must be a way to ignite the compressed
mixture atthe right time.

If all three things are present, the engine MUST run.
It maynot run long and it may not run good, but it
will run. Always remember that!
The reason I say that is because engines can do funny things.
Sometimes things that shouldn’t work…work. Other times, things
that should work…don’t. We need to remember that
there is a reason why it works and why it doesn’t
work. If you did it all right then it MUST work. If it
doesn’t work…you did somethingwrong. When things
don’t work, remember these three things and go back
anddouble check your work.

In an engine these things occur as part of a cycle.
That cycleis basically this -SUCK, SQUEEZE, BURN, and
BLOW. The fuel mixture must bebrought into the
cylinder -SUCK, compressed -SQUEEZE, ignited -BURN,
and thenexpelled from the cylinder -BLOW. All
reciprocating engines must go throughthese steps no
matter what the design of the engine ( two-stroke,
four-stroke,whatever ).

In a Four-Stroke engine the intake valve opens and the
pistongoes down, sucking the fuel mixture into the
cylinder. The intake valve thencloses as the piston
comes back up squeezing the mixture. Spark now occurs
andthe burning gases expand, pushing the piston down
with lots of power. As thepiston comes up again, the
exhaust valve opens and the burnt gases are blown
outof the engine and the process starts over again.

This is all done in four strokes of the piston.
Piston down… Piston up… Piston down… Piston up.

In a Two-Stroke engine the piston goes down,
compressing thefuel mixture under the piston and
blowing it into the cylinder. As this mixtureblows in
it also blows the burnt exhaust gases out. The fuel
mixture is blowninto the cylinder through passages (
Ports ) in the cylinder walls. The pistoncomes up,
covering the ports in the cylinder walls and
compressing or squeezingthe mixture. This also creates
a vacuum in the crankcase under the piston,sucking the
fuel mixture into the crankcase. The spark then
ignites the mixtureand the burning gases push the
piston down, starting everything again.

This is all done in two strokes of the piston.
Piston down… Piston up.

That’s all there is to it. There are other engine
designs butthey are not used much. The rotary engine
was used on several makes ofmotorcycle, but not many
were made and they all have been gone for many years.

may the wind be at your back and all your roads be twisty