a wet clutch requires a different blend of oil than regular automotive oil. The proper answer to your question is - what does the owners manual say.
You can get motorcycle oil at Autozone or Oreilly with brands by Penzoil, Castrol ect. You don't need much as the frequency of change and quantity are low for a motorcycle like that.
Japanese bikes have a "JASO" oil recommendation, the Japanese "API" to our API, try to follow that.
(From the web)For 4-stroke gasoline engines, the JASO T904 standard is used, and is particularly relevant to motorcycle engines.
