I try to keep a log book of the work I have done, date it, and sometimes make notes of stuff I did or need to do.
At least this way I can look back at when I did the brakes, or the vacum lines, or replaced fuel lines, or any wiring crap, so at least I can keep track of it all, memory is still here, but time pass by fast one month and slower another, so a year could be yesterday or weeks ago to me, LOL.
Yes it is a process, and one can only go thru the list above and see what they find. Some are simple inspection checks, others take a bit more time, but you could find/isolate the problem in a day I would think. Getting older worn out carbs to work is a pain and hard to get parts for on some models. Hope you the best.