I have a gallon of carburetor cleaner with a basket inside it. It dissolves most things within a few hours, including plastics and rubber. It is the most vile smelling stuff I've come across but it works. IIRC, it was cheaper to purchase than a couple of pints of acetone at today's prices.
Some issues I've had with cleaning carburetors is that the undissolved blockage in main jets or orifices may be hard mineral (AKA, that piece of sand that gets transferred between fuel storage tank and equipment fuel system). I can see where an ultrasonic cleaner would shine in that case.