Cleaning carburettors using an ultrasonic bath is undoubtedly the best way to clean carbs. Particularly when they've been standing, & the petrol within them has dried to a rather nasty 'gunge, which blocks the jets & the small air passages within the carb body.
However, due to the cleaner in the bath being water based it is imperative that all traces of the cleaner are removed from the carb body, for it will cause the body of the carb to corrode, & you'll be back where you started only worse!
After removing carbs from the tank I squirt a water displacing fluid, (like WD40 on steroids) through all the passages, then using a high pressure airline I force air every which way through all the passages to remove it & any water within. I repeat the process using brake cleaner which removes any residue from water displacing fluid.
Every component is then inspected before the carbs are re-assembled, I set the floats to their correct setting, & finally fill them with petrol & leave them standing under a good 'head' of petrol for an hour or so to ensure that the needle valves are sealing properly.
There are many postal carb cleaning services. Some very good, & some not so good. I have had the misfortune to have had to de-buggerate carbs that have been sent away, & obviously worked upon by someone who doesn't know how a carburettor actually works!
The prices for this service vary considerably. Not least due to the number of carbs involved. Please call for a quote.
NC30 Carbs. Standing for 5 years.
The same NC30 carbs.