What causes pistons to loose compression?
To expand on this, a compression test of a cylinder of a 4 stroke engine (an engine with intake and exhaust values) may lose compression due to worn piston rings caused by friction (and/or) values that do not seat properly. When the piston comes up on the compression stroke both valves should be seated tightly in their respected valve ‘seats’ to maximize the compression. The loss of compression may be due any or all of these parts.
