that is correct, The valve keepers and springs are located behind the breather cover, behind the fuel tank. You adjust the valves on the old flat heads, by grinding the valve stems to obtain the correct setting. Normally they will also wear a groove in the valve face, that will either have to be cut out or just replace the valves, but will have to be adjusted for length, and also lap into the seats.
If both valves are closed when you remove the head, take your thumb and press down,while turning to see if they turn easily. If they turn easily then they have worn, stretched, and will have to be redone.