I have an ultrasonic cleaner, I cleaned the carbs offof my '81 R65 about 3 years ago .
I used a cleaner specifically for use in ultrasonic cleaners for cleaning aerospace aluminum .
I was less than pleased with the result, while the surfaces were clean, the aluminum was darkened quite a bit .
Also, I'm not so sure how good a job an ultrasonic cleaner is on small passageways like the Bing carbs have .
Ultrasonic cleaners work because of microscopic bubbles in the cleaning solution collapsing and sending out shock waves, the shock waves are what do the cleaning .
If the cleaning solution is not in contact with the blockage (inside the passageway), no cleaning action will occur .
If you do find something that will brighten the aluminum while in an ultrasonic cleaner, please post it, my '84 LS carbs are in need of a good cleaning/brightening .
If you like, do a generic search for ultrasonic cleaning principles, and you'll get the general theory behind it .