Cycle oil leak

Old Yamaha's are like British bikes; you gotta expect the mess; it's just a fact of life. The older the Yammy, the worse the leaks were.
Is your second gear still working?
If yes, the day will come when it will start jumping in and out, and that is the day you can strip the engine down and fix the seepage.
The sealer to use is a 3M product, that you can buy from the dealer as Yamabond. Clean it right and thatchit will seal her up for a long time.
In the meantime, put a pressure gauge on the CC and make sure it is not building up pressure.

To patch it, you can use a gas-tank sealer, called Seal-All. But you will have to clean the heck out of the area. This won't be pretty, but it is removable at a later date.

You cannot use JB because as the engine heat cycles, it shrinks and grows, and sooner or later the JB will chunk off. But long before that happens, the leak will find it's way around the delaminating JB.

Good Luck