I need to go through a couple of carbs. What is the best chemical/solution and or procedure for soaking the carb bodies to get all the passages as clean as possible. I don't want to damage the aluminum or gold-cad finish on the linkage. I've read more than one place that boiling lemon juice works wonders. Any thoughts?

If it's an Eddy you could soak the small internal parts seperately by themselves & with the carb upright pour some soup into the carb bowl to clean the internal passages so the outside stays pristine. There's no metering in the top so you could clean it with something that's non toxic to the finish/same with the outside linkage. this also lets you get by with purchasing a smaller amount of cleaner as you dont need a big enough bucket for the whole carb to fit into

I use this stuff, it's only 50 bucks a gallon. Works great and I have done 2 carbs and 3 spray guns with it now.

Tricky to get one absolutely clean using only chemicals while protecting plating. Lemon juice cleans but contains citric acid which will likely eat your plating. Id try the mildest cleaners possible and go to more aggressive cleaners only as needed. Start with Simple Green, it works great in most cases.

He also asked what to use that wouldn't affect his plated parts. I simply suggested a product that I know to be safe on his plated items.

Never noticed any plating damages to either spray guns or carbs.