Thes fuel valves are a great concept - but as most find out - can be a PITA.
On gas engines - especially .
The diaphram pump in the Walbro type carbs, require a solid head of fuel, to operate properly.
a loose fitting fuel line on a tank is enough to stop them from operating .
the fuel valves -which can seep air a bit, will cause starting probles etc.. which are seemingly impossible to detect.
Anytime I get asked for help ona new model which "won't start"-- the first part of the questions is - what did you do for a tank/fuel fill setup .
99% of all these problems is in the tubing connections and filler /filter setups .