You can do a basic test on the metering side of cube carbs. Some are easy and some not so easy. If the carb has a purge bulb apply 7 psi to the fuel inlet and when you pump the purge bulb the pressure should drop slightly with each pump. If the carb has a nipple that connects to an impulse line you can connect a short piece of fuel line and a purge bulb. After pressurizing rhe carb pump the bulb and the pressure should drop a little with each pump. Some carbs just have a small hole for the impulse. I chuck those in a vise to hold it and pressurize it and then hold a fuel line with a purge bulb tight over the hole and pump the bulb to actuate the metering diaphragm. Tricky but can be done.