So, after many other projects that caused the 500 to be back burnered, I’ve finally found time to start bringing my ‘73 back to life, but horror of horrors, I can’t find all the parts. 
All those parts were carefully stored in zip lock bags, some cleaned and some needing closer examination. Buy where did they go??? More on that as things progress.
I’ve also accumulated some spare parts that I’ll start sorting, cleaning and storing, Carefully! I’m going to get started rebuilding the carbs. I found the originals and have three other sets that I intend to rebuild, which brings me to a question.
Where is the best place to get complete rebuild kits for ‘73 cb500 carbs? I’ve been away from repairing bikes for decades and I’m out of touch with the best suppliers of quality parts. Your help will be appreciated.
AFAIK, there are no 'correct' parts kits for either the CB500 or the CB550 carbs today. The best bet is to obtain the O-rings and possibly some new float valves (check at PartsNmore.com for those) as parts. The jets, needle jet, and jet needle DO NOT need to be replaced: merely cleaned well. All of the aftermarket kits I have seen in the last 10 years are using Keyster brass parts and jets, which will not work well (if at all) in these carbs. If you end up needing new jets, get the genuine Keihin type from JetsRus.com. They don't have the correct jet needles nor needle jets.
If you can spend the $$, get the "carb cleaner can" from NAPA auto parts, about $25 here for a gallon can with the little basket inside. This stuff has been the best I have found for these carbs' parts and bodies. Lacking that, Acetone works well but will raise a dark surface on the carb bodies (when soaked in it) that you have to remove by hand, takes a while. I soak them for 2-8 hours in either one.
If you are forced to use the Keyster jets, they run about 7% leaner than the number stamped on them, as compared to Keihin's jets. This is mostly due to the taper's change in the fuel venturi, changing the feed at speed: they get leaner as the RPM goes up, causing lots of throttle issues.
