Here are some of the possible places where leaks can occur:

Fuel line ends in fuel tank
Fuel tank stopper
Brass tubing in fuel tank
Fuel line in the tank
Fuel line to remote needle valve
Fuel line from rnv to carb
O ring under carb

The fuel line from rnv to carb seems to always get overlooked. A clunk can turn to the front of the tank and get stuck.

Edit to add leaks from backplates