Can perhaps help out on that one.
When the fuel tanks are full it takes about 11 seconds to drain all the fuel in one of the lines between tip tank and fuel strainer and about six seconds to drain all the fuel in one of the lines from a main tank to the strainer. When the tanks are less than full, it will take a few seconds longer.
Don't forget that the fuel selector must be positioned in the folllowing sequence.
Off, left tip, left main, right main and right tip.
This is to ensure that the fuel lines between each tank outlet and fuel strainer are drained as well as the strainer.
Hope that help!
Toodle Pip!
