They call it a 4 stroke compression test because you unhook the spark plug wires and crank the engine 4 revolutions. By that time pressure should have gradually built on the guage. I remeber I did mine and they where like 90-120. Then I squirted some oil in the cylinder to get a better seal and it started reading 120-150. So I had great compression. When I took the block apart I saw that the head gasket was letting oil into the cylinders. But I replaced the rings just to be safe. Runs great now.