What is an Air Cut off Valve, how does it work, how do I check it?

VFR 750 FV (60,000 Miles)

Petrol started pouring out from somewhere under the tank from the carb bank when the engine was running, stopped when engine turned off.

I Have removed the bank of carbs.

I suspended the carbs and poured petrol into the deliverypipe to see if I got any leaks. I got none

Have removed allowable jets and have removed the 2 easy 'Air Cut Off Valves' which sit on the side of two of the carbs.

Questions?

1) What is an Air cut off valve, what does it do?

2) How can I tell if its working or not?

Should I go the whole way and split the carbs and make them separate with the hassle of all the pipes and new O rings or just clean the carbs and replace the float valves?

Any guidance appreciated

 

https://www.youtube.com/watch?v=Jb6gckj_saw I found this on YouTube. I personally don't know anything about them.

Also this http://www.goldwingfacts.com/forums/2-goldwing-technical-forum/340076-air-cutoff-valve.html

 

I would want to know why you removed the carbs if you had no idea where the leak was coming from, a fuel bottle is the way to check

 

Because I could see fuel dripping out from within the carb bank.

Because there were no splits in any fuel pipes leading to and / or from the carbs

Because I could not properly check all the carb block without removing them.

Because I just inherited a 60K mile bike and want to inspect the carbs properly especially as there was / is probable a fuel bowl leak...

 

Ok so if you have pulled the carbs sit them on the bench and hook up a fuel bottle so you can see where the leak is coming from, probably stopped by now because the seals have swollen up and 60k isn't much to worry about

 

Thanks, good video..

 

Did that, used a funnel rather than a bottle, no leaks. would the pressure of the fuel pump be exposing the problem, which isn't evident under pure gravity?

I think I am going to soak these babies in paraffin an ease the dirt off and leave the other air cut off valves in place. Don't fancy spliting those carbs, pipes look fragile to me. Buy some new O rings, float valves and bowl gaskets and put it back together again fortunately diafragms look ok....

 

Pull the bowls, clean the jets and put them back together, try and avoid problems that are not there then retest with funnel, the fact you have put fuel in the carbs means the seals will have swollen up and hopefully they will be sealed now