How to change the tire valve cleverly?

Due to the long time of use, the modified valve will leak. If there is a slow tire leak or a valve leak, it is often encountered.

When the valve leaks, it can only be replaced. The leak is usually the leather gasket under the screw.
Before installation, handle the sundries at the position of the steel ring valve installation hole and polish it smoothly.
Then cut a section of the valve part of the previous old inner tube, and cut a circle around the valve mouth with a radius of 2 cm.
Two rubber rings of the same size, one circle is installed on the valve, and then installed on the steel ring, and the other is on the valve outside of the steel ring, and then the valve screw is installed. Some sealant can be applied around the valve.