Do you have some good tips to clean the brass and tank without destroying the brass or soldering or the zinc too much?
The brass float is broken with several broken parts as shown in the image
I think I can repair it with soldering.
My rule of thumb on cleaning anything is start with the least aggressive thing you have and if it doesn't work go to the next. Things that won't damage brass or pot metal would start with soap hot water and a soft toothbrush. My next go to is either alcohol or GoJo hand cleaner. Alcohol will corrode aluminum but but has to be left with it siting in it like a carb bowl. GoJo doesn't seem to bother anything, you can use it on your clothes then run them through the wash. If all that fails I resort to carb and choke cleaner which won't usually hurt anything either. Brake cleaner is pretty harsh but I haven't had it damage anything except paint. Another thing I have found that will clean some corrosion is EvapoRust. I haven't had it damage anything but also haven't tried it on any fuel related corrosion. It doesn't seem to damage anything but some things it won't affect at all. If you use it rinse well or it leaves a sticky residue.