Gear oil, as above or 10w30 four stroke motor oil with no friction modifiers, or Automatic transmission fluid type F or a motorcycle gear oil designed for wet clutches.
As to 2 stroke oil, do not use cheap oil which is used for weedeaters, chainsaws or outboards.
The 2 stroke oil should be designed for air cooled motorcycles and beware of your choice if you are running oil injection, some oils are designed for premix only.