If you want to clean your carburetors without breaking the bank down to the individual carburetors, I would buy a High E acoustic guitar string from a music store, and a can of carburetor and throttle spray. You are going to want to shoot a good spray into primary main jet, secondary main jet, primary slow air jet, air cut off feed, air bypass, primary main jet, slow speed jet, float valve seat, accel pump feed hole, pilot screw hole, and secondary main jet. Then run your E- string though the slow speed jet making sure it is clean; it should go down and 1 ½ in from the top of the tube. After you have cleaned these, you will want to wrap tape around your carburetor and throttle spray straw to make a tight fit into the slow speed tube. Hold a thumb over the primary main jet hole a finger over the low air cut off hole and spray. If the hole is clear you should get a spray out of the pilot hole. Also, make sure your accel pump on carburetor #2 is not clogged. I make the accel pump action on the tube coming through the carburetor with a little gas in the bowl. You should get a squirt of gas out of the brass square on top. There are many other things to check, look for, and clean that make a good carburetor cleaning and rebuild, so I will add the link that I feel helps everyone who has ever tried to clean the carburetors for a DOHC CB750. Follow the directions and you should be fine. You might need to get 8 new screws for the choke plates if you decide to break the carburetor bank, they usually are not reusable. Sweet bike and welcome to the forum, also check into bypassing the air cut offs and getting new O-rings at least.
PS: I agree completely with Piute, your taste and effort will change over your build. Minimalist changes to appearance and more changes towards maintenance and performance is the best way to go. Don’t let me persuade you though. I rushed into painting my frame and motor and the minute a little gas gets on it I want to cry. lol It wont stay perfect unless you don’t touch it again.
http://www.cb750c.com/publicdocs/SeanG/Honda_Carb_Manual_revE.pdf