How about doing both. I think whunter's suggestion of the spray chain grease is a good idea, but what about combining that with putting the caps back in with one minor modification---center and drill a tiny hole in each cap so that water can wick out if there is condensation that develops or any water happens to "splash" up in there. Then I would think you would have the best of both worlds. Just a thought.

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1986 300SDL
1988 Monte Carlo SS
2002 Avalanche
2003 100th Anniversary H-D Dyna Wide Glide