Originally Posted by Nashville Kat
I've been sitting here with a jug and an old piston in my hand-
yes, your comments are right, and the flaw in my own thinking was that the top of the piston cleared the intake port- but it never does-
yes, all of the intake is drawn in a roundabout way through the slots at the bottom of the piston and not at the top- the bottom of the piston clears the intake port, but the side slots in the bottom of the piston clear the side ports only at the very top of the piston stroke.
It appears that the piston never really clears the exhaust port at any time, top or bottom, so that all of the exhaust exits through a side port and then goes to the exhaust port through the jug.
The piston drops below the exhaust port on every stroke, the engine intakes, compresses, combust and exhaust on every stroke.
A four stroke engine combusts and fires every other stroke, it has an intake and compression stroke and an exhaust stroke, valves and timing determine all of this.
On a two stroke engine it exhaust everytime the piston is at BDC and compresses and fires everytime the piston is at TDC.