Once you get something between the piston and bore , for example, you have NO NEGATIVE PRESSURE FORCES with which to expell it...
The exhausting of gases is from the upward movement of the piston ... and thus is also a downward force on the area around the side of the piston.. which keeps anything at that location locked in place...
I can't believe a grown man would throw me such a softball ... of course it makes more sense after your derivisive comments about me following the Factory Shop manual...