Hello, and what is the score with leaking 'wing nut' fuel tank caps?

[Ratty]

Hi all, and thanks for letting me join your most excellent looking forum! I fully intend to get involved and offer as much to the forum as I may take from it, so huge apologies for being on the latter end of this from the start, but;

How do you get a good seal on a 'wing-nut' type fuel filler cap? I have a breathed on M100 Panther, and I love it to bits, but the filler cap leaks like a !"£%^% with anything more than half a tank. Partly I can put this downtown vibration, but they can't have been this bad when new, so what have you all done to get a sealable filler?

I've made sure the hinge is angled right, so the cap fits flat to the filler neck, but it still loosens with vibration. Do I need a better rubber gasket? Or is this just an incurable problem that will only be resolved with a different tank cap?

All input gratefully received 😉

[R]

When you say 'loosen off' with vibration, does your inner workings of the cap have the spring action to it,
such that when you snug down the wing nut/bar, it feels like it sort-of locks down, and then shouldn't move.

Also, my cap has more of a fibre type ring seal to it.
I've seen it said these should be boiled up before use, the moisture then makes them fuel-proof.

But maybe we haven't experienced panther type vibrations, so who knows !!?

Welcome aboard.
Cheers.

[john.k]

i think these caps originally had a cork seal,which is softer and more resilient that rubber......the cork is fuelproof and easily conforms to the gap without force being needed.

[rgsjohn]

Not sure what the answer to this is. On my RGS the tank cap has always been incontinent. I have tried various different materials to seal it. It originally had a rubber seal. So far I have found nothing which works very well. I have just learned to live with it. I just try to avoid sharp braking and bumps when the tank is brim full.

[mini-me]

If its the kind I think it is, with 3 little gizmos expanding inside the filler neck, you will find that the neck is stretched over the years, I have the same problem with pie crust fillers on AMC.

Make a gasket out of soft leather if poss or make up some kind of baffle.

I did once have an idea for an insert and threaded filler, but it was beyond my skills to finish it. Now I never fill past the critical mark.