Perhaps ultrasonic cleaning is a mystery to you. You've heard of it, but it remains "out there", unknown and considered only in terms of hyperbole and folklore.
Sometimes folks refer to ultrasonic units as vibrating machines. No. They do not work by vibration. If you understand boat propellers, you will understand ultrasonic cleaning. As a boat prop spins in the water, the shearing of the water actually slowly wears the prop's metal away, especially at its base. Boat techs call this "prop burn". It happens because the water the prop churns in cavitates. That is, oxygen in the water is abusively removed, cavitated out, from the water by the prop's movement, with the result a very forceful impact on the prop over its surface, steadily "sanding" away its metal. An ultrasonic machine works in much the same way. The ultrasonic machine's tiny cavitations, much smaller but more numerous than those happening around a spinning boat prop, and created by uber high frequency sound waves rather by than a rapidly rotating part, vigorously scrub the carburetor's surface in the ultrasonic cleaner's tank. The result is clean you have to see to believe. I have to change out my detergent every two weeks, before the dirt builds up like the slime on a creek bottom. So, cavitation, not vibration. And boy does that cavitation work!
Ultrasonic at various power levels is used to reclaim TVs from smoke damage. It's used as the final manufacturing step in computer parts assembly. Engine builders clean cylinder heads using it and gunsmiths firearms. Yet ultrasonic gently cleans jewelry too. Pretty amazing stuff.
There are a number of things you should know before buying an ultrasonic cleaner, and they almost all relate to how some manufacturers basically try to cheat you.
Wattage. When looking at wattage ratings attempt to separate the heater's wattage from the transducer's wattage. Manufacturers like to combine them for more impressive numbers in the brochure. Not only is this deceptive, a heater is an unnecessary expense, as anyone who has been around ultrasonic machines knows. And as for recommended wattage, pro work starts at the 250-watt point. Anything less is dabbling. To put it another way, $3000 is entry level for a carburetor cleaner. If that Harbor Freight unit cleans your carbs, then so would dunking them in gasoline. Seriously.
Capacity. Capacity is another slight-of-hand deal. A 10 gallon tank seems impressive, but not so much when you discover that the manufacturer achieved that volume by building the tank tall instead of wide. A too-tall tank moves the workpiece farther from the all-important transducers at the tank's bottom, making the sonic waves pass through more water, dissipating their effectiveness. It also leaves less room for the transducers, meanng too few are used, making the unreasonably deep tank less powerful for that reason as well. The best tanks are wider than they are tall. But these tanks aren't cheap.
Frequency. Wave frequency matters. The cheaper units run in the higher frequencies, typically 42-50 KHz, while the better systems run in the lower ranges, 25-40 KHz. A 45 KHz unit is for jewelry, a 25 KHz is for engine parts. Carburetors are best cleaned somewhere in the middle where the frequency is high enough that the waves get inside tiny carburetor passages, yet low enough to produce waves with the scrubbing power needed.
Chemicals. It is well known that ultrasonic machine makers try to make a killing on the cleaning chemicals they recommend and sell. Equally well understood is that in response, every ultrasonic user quickly discovers his own alternative, and that no carb rebuilder wants to divulge his secret formula. Forget Pinesol. If Pinesol will get your carbs clean to your satisfaction then so will paint thinner. Seriously. But neither is actually very effective, and more importantly, neither is safe in ultrasonic waves. Fire hazard? Better believe it. Think microwaves. Most carb rebuilders use some form of detergent in their ultrasonic units. You have probably heard of folks using Simple Green. But while it is a powerful detergent, you should know that pros don't regard Simple Green as an acceptable cleaner. Its high PH is reactive with aluminum, creating white fuzz on the carburetor bodies. Dilute? Well, you'd have to get it far too dilute to be effective.
Disassembly. Although there have been some folks promoting it, it is bad practice to try to take advantage of ultrasonic's cleaning power by not disassembling the carburetors. They must be completely disassembled. For one thing, left assembled, pockets of water will remain inside the carburetors, and this will react with the diecast aluminum main bodies, corroding them.
Incredibly, a few carb rebuilders have spoken out against ultrasonic cleaning. Without ultrasonic, you will necessarily be exposing yourself to chemicals that are carcinogens and known neurological hazards. Without ultrasonic you must find separate ways to clean plastic, rubber, steel and aluminum parts, not to mention tiny springs and diaphragms, all of which are safely and thoroughly cleaned by ultrasonic. Without ultrasonic, you are avoiding the very best way to free corroded-together parts. Without ultrasonic you have very limited options for removing minor oxidation. And without ultrasonic you miss the pleasure of seeing freshly cleaned carburetor castings glisten prettily almost as when they were newly made. Great stuff, ultrasonic! Coming up in the business as I did, I used the methylene chloride and other dunking chemicals long considered the only way to de-varnish a carburetor inside and out. Then I decided to give ultrasonic a try. I will never go back.