For years i have used lemon juice and water mixed 50/50. Put it in a pot and simmer just below boiling, but do it outside if possible, stinks a bit.
I have used this on motorcycle carbs many times, never ceases to amaze me how well it works. John
The whole bottom section of my 1904 was pretty bad, including the throttle plate. I let it soak for 48 hours in a 50/50 mix of water and white vinagar. use a plastic container as it will eat thru tin trays and such. (don't ask, but my work table still has the marks) I used a large plastic coffee container. some scrubbing with a brass brush, rinse well with water, and she was good to go. Use compressed air to blow it dry really well including the few small passages. Be sure to have the little check ball and such out. I left the throttle plate in place. Definitely an outside project.
Ditto on the vinegar and water. It cleans the corrosion up fairly well. It works faster if you have a way to heat the solution. Just keep an eye on it though. It could probably eat the castings up if the vinegar was too strong and it was left in for too long.