engine runs then stalls

[twiss]

never had a problem with mine like that...

bearing in mind its a 99p ebay valve... so i wouldn't be surprised if it doesn't even have a spring in it
maybe it allows a bit of air through as there's not enough pressure to close it

[ScottieJ]

It's not a problem The float chamber vent is supposed to be open to maintain atmospheric pressure, it must allow air to enter the float chamber as fuel is used and air to escape as it fills up

Which way around do you have the valve fitted?

[twiss]

the valve is fitted to allow fuel overflow, but its pointing downwards so its probably not shut

it will shut off if liquid goes in there though!

edit:
ive just taken it off... when you hold it so the direction of flow is pointing downwards away from the carb you can blow through it gently without shutting it off... if you blow through it harder it closes
when i lower it into water with a hose on each end it doesn't let the water through but i can blow bubbles down through it
i think the key is a cheap valve

[ScottieJ]

What happens when it's running and you block the pipe off though?

Doesn't matter what way the valve is if it's dunked in water it's not going to allow air either way

There isn't enough vacuum for it to suck water up, well there isn't really a vacuum at all, just needs to be able to breath

[twiss]

Mine still runs but it slows the idle... maybe worn needle valve
If my valve goes underwater it wont let any air out but it wont let any water in
and when the water is over your bonnet the water can get in there