I have a 74 superglide with fatbob tanks.I just put the tanks on after repainting.I also put new gas caps.
Is there a way to tell if the vented cap is working properly?? When I take off the cap (either one) you can hear the air escaping,sometimes rather quickly.Is that normal or do I have a faulty vent cap?
I would try my old cap.....but I think I threw it away...live n learn....
Thanks in advance for any help

 

The left side gas cap is not vented. The right side cap should be vented. It sounds to me like there is something up with the right side cap. Have you pulled the cap and inspected it to ensure it is the vented type?
I have never heard a rushing of air when opening up my gas cap.

 

I did check the right side cap.It is the vented style.It has what appears to be a blue "valve" in the middle of the bottom side of the cap.
I didn't know if there was/is a way to check the cap to see if it is working properly.I took it off and messed with it a lil and put it back on.Seems to work fine...for now.But,I haven't ran the bike any either.
Thanks for the response.

 

I'm thinking that valve on the cap is just to let air in as fuel is used but it doesn't allow the tank to vent to atmosphere. I would not want pressure building up in my gas tank(s) because of engine heat or the sun shining on the tank. Myself, I'd look for a cap that just has a vent hole, not a check valve. Maybe you could just pull that check valve stuff out of the cap...
Hope you get it resolved.

 

I had a similar problem, but it turned out to be a blockage in the upper vent tube in the left tank. Make sure you can blow thru both vent tubes.
Just my two cents.