Petrol tank cap seal material?

[charles.bulloch]

Graham, the 56 tank is different, it has detachable flutes and a smaller filler cap.

Charlie

[john.bebb]

Probably the best gasket material for a relialbe and lasting seal is sheet neoprene.
Easily cut & trimmed with sharp scissors or blade
Readily available and not horrifically priced. Cheers, John.