[Richard Farrant]

Originally Posted by Lynn Eades

Richard, after a quick read, the spark arrestor in the Australian carrier tank, is the mesh strainer, not the valve.
The non vented cap should not have the hole that has been drilled in it. I expect that it has been used on a tank with no vent pipes.
Ben the valve is in the cap, and is closed by the movement of the steel ball.

Thanks Lynn, that all makes sense now