Click spring is right on. Oil verses WD40. For over 25 years, I made a living repairing electric organs. Many of these instruments were the old Hammond tone wheel. Basically a clock motor connected to spinning ac generators that the selected signal was amplified. To oil, you use a fine grade non gumming oil sold by Hammond. Never ever use WD40. The amount of oil was important. Too little and you hear a bearing squeel. Too much, it would get in the electronics. Either way, I had to fix it, the latter of too much oil was the worse and most expensive.