From the diagram attached, the spring on the check valve will determine the amount of pressurized oil to the front bearings before it is forced to the tank when the valve finally opens. It's pretty clever actually! Just a small adjustment on the spring will enable to build more or less pressure inside the engine to lubricate all the moving parts. There is always the piston ring for when the pressure is excessive, giving some margin for error.

But from the main topic, I thought it was a fully enclosed system, i.e., no externall oil tanks, all contained inside the engine - of course, this method would need a different ring to prevent oil blow-by from the sump to the combustion chamber.

Good job hamaoki![8D]