OK, now I understand too. And to answer your question I believe that most stickers are applied w/ an adhesive of some type. And most of these adhesives can be removed w/ several petroleum-based products like WD40, lighter fluid, Goof Off, etc... I don't think these will adversely affect the inner part of the cap. But I also believe that the remaining adhesive will not affect the cap's operation, so why not just leave it alone?

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