Ok, so you know the drill. you shake the carb float and cannot hear anything that sounds like liquid. You float it in a cup of liquid. is it really OK? Not necessarily. I was inside an old forrest gump Snapper rider carb and it has sat for years and years. The carb has a little brown goo in the bowl, but it cleaned up well as did the float with a bit of lacquer thinner. I had no reason to suspect a bad float, but this is a sure fire test. If there WAS any old gas inside the float, it probably would be pretty thick anyway, so I did my test.
Just run some hot water as hot as you can stand in a container and immerse the float. The metal heats up quickly and causes the air inside to expand ----. bubbles happen pretty quickly. Just for fun, i immersed the float into cold water, and quite a bit of the water sucked back inside the float. Very evident that the liquid got inside. It rattled a treat.
I just watched a video that has 35k subscribers and the guy is pretty good with carbs, and the guy just threw the float in a container of gas and it floated. He called it good and went on. My old float floated just a high as his float did, BTW. That's why I am sharing this here. BTW, you can repair these floats with solder in a pinch, but I buy new ones if it is possible. i dry out what is inside by setting them outside on top of an incandescent light bulb well away from a building and then after they boil dry and quit spewing fumes, use solder or gas tank liner to fix them..