Looks like a one way valve ,it may just work by holding vacuum in the choke diaphragm when you turn the motor off otherwise when you started a hot motor the choke would be on , it may take half an hour for the choke to close with this one way valve when you turn the motor off.
That's a guess as I can't see the carby or the diaphragm .
I'd just get a car windscreen washer one way valve and use that.The Volvo one would need one hole blocked.
