E string from a guitar can work on some of the jet holes... Honda sells a jet wire kit designed for cleaning the carb holes... Expensive but, it will not damage the jet holes by forcing a wire that is too big...
Sometimes the Zinc alloy in the carbs builds up in the jets, it needs to be cleaned out...if you can chase the tiny passages with compressed air, a wire, and carb cleaner it is good. If you have access to an industrial Ultrasonic machine, even better. The brass has to come out before cleaning any method you use.
But, it sounds like you have the brass out.
Does Sirius Consolidated in Canada have the PD42 carb parts?
How about mother Honda? Granted the later is only going to possibly have the stock jet sizes.
Post your solution if you find one, Hopefully, someone will step up that knows the CB750 carbs you are looking for and can point you in the right direction. There is a thread about 78s on the site...
Bunch of 78 owner of 750s and 550s They are likely to know your answers. Google search and use "site:forums.sohc4.net" in the search string.
David
