Lawnmower Fuel Shut Off Valve Install - Protection from Ethanol Gas damage

In this video I explain my theory on why ethanol fuel turns to goo in the carburetor when left sitting for a long time.
We'll add a fuel shut-off valve to my walk behind string trimmer. This applies to any small engine with a gravity fed carburetor.
At the end of the season I'll use this to shut off the fuel supply, then run the engine to drain the float bowl, before putting it away for storage.