Would I need to replace the brake shoes on a VERY old motorcycle?

I've got an old Honda PC50 moped (1976) which has only been driven around 5250 miles and hasn't been driven since 1992. I haven't got her started yet, as I'm waiting for the spark plug removal tool to come in the post so I can sort her out, but I have noticed that when I apply the brakes, there seems to be NO effect whatsoever, unless I press them EXTREMELY hard. Anyway, I don't know anything about motorcycle brakes, but since they're drum brakes I imagine they work the same way as the brakes on an 1930's tandem bicycle I have... Which still has the original brake shoes, working perfectly.. I was wondering if I would probably be able to make these brakes safe again with a bit of adjusting, or would you say that time has rendered the shoes unsafe? What exactly are they made of, anyway? Anything that decays?