Here is some advice from air-cooled VW forum – Volkszone, where more tips and fixes are available.
If you need to adjust the idle speed its the large screw on the side number 3 in the picture. 2 is the mixture and 1 is the fast idle adjustment. Adjust when the engine is up to full temperature.
Flat spot issues
1500 single port refuses to start seems to be flooding, was running okay-ish then seemed to run at very high revs cut out now not starting but very Strong petrol smell in engine bay, carburettor problems maybe?
I have a 1969 Westfalia 1.6 single carburettor. The last few times I’ve taken her out she has run very sluggish especially when I change up, seem to hit a flat spot. After a few miles she seems to sort her self out and run ok. I had a split in the air pipe but duck taped that up. Always starts on the button, just when driven cold she seems to play up. Choke correctly set? Carb Icing? All hot air pipes in place? Heat riser getting hot? Air leaks? Gaffer tape is not OEM fitting.
I’m having to replace the battery tray in my ’70 bay. Looking at it, the area doesn’t appear to be structural other than to support the battery. With this area being particularly prone to rusting (here comes the stupid bit) is there any reason it can’t be made from wood or heavy gauge perspex/plastic and bolted in? It would stop the rot.
The battery tray is a 5 mm thick fibre glass insert, bolted to steel angle iron around the edges. Good and strong, and rot free.