The older one must be hard to read, there is no AR2-14 size offered by Gurtner and reglage 488 is specific to the AR2-13, the reglage numbers are not repeated.
AR13 488 O 11/61 means it was produced on line O on November 1961
AR14 488b S 5/62 means it was produced on line S on May 1962
Gurtners need to have the needle valve surgically clean, so if the float seat has any dirt it will either not flow or not stop flowing. You can try blow air some gentle into the seat and check the point on the needle is not distorted or has a step worn in it.
Fuel will flow into the carb via the little auxiliary filter/sediment trap chamber then to the fuel bowl. Check the gauze on the saran filter in the sediment chamber is not falling apart and shedding little pieces of plastic.
Check carefully the brass jet, there are holes to the side of it as well as the hole that unions with the diffuser, the diffuser also has a couple of tiny tiny holes that need like a single strand of house speaker wire to chase out the hole.
There is no real 'gasket' kit for the Gurtners, there is only the figure 8 gasket for the fuel bowl/sediment trap and the fiber washer at the nut that holds the lid on. The figure 8 gasket needs to be good at the sediment filter portion of it but for the bowl it is just to stop fuel from sloshing out.
Here is pictures from the AV88 manual and the Gurtner catalogue so you have a visual reference. Hit me up if you need some of the frenchie translation for the parts or maybe a explain of how something operates.
Brian Aplin likely has the figure 8 gasket in stock andthe little washer under the nut, hemay even have a new jet if you need that...