A manual fuel shut-off valve
is required for safe operations

This valve should be closed at all times except during normal engine operation. It is especially important to close it prior to fueling the model.
The manual shut-off vavle should be located such that it is easily reached and closed if a start sequence goes awry.
If you suspect that the engine has excess fuel in it prior to a start, purge the engine as necessary, then begin the next start sequence with the valve closed. If all is going well during the start, open the valve slowly.
Make it a habit to close the vavle at the end of the engine shutdown procedure. BVM #5315