You can always try... Nothing more to loose than a few hours.
To clean all the jets and all things brass inside a carb I had great results with dropping these parts in hot (nearly boiling) water with a good splash of liquid copper cleaner. It smells terrible but as long as you don't inhale the fumes there's not really an health issue I think. Work outside.
Drop the pieces in the water/copper cleaner mixture, shake well for a few minutes and rince afterwards. I had jets which had turned completely black and they came out shining like new. Even the inside of the jets. You may need to repeat this procedure as your jets look really clogged up. You might wanna try opening the jets first with a fine needle or thin wire. I used a few threads from a battery connecting cable, lots of fine wires in there and you can take just as many as you need. On top of that, they're made of copper so little risk of scratching the inside of the jets.
Rubber parts: seals and O-rings; don't try to save them, just buy new ones.
Floats: drop them in water with a few drops of soap and keep them submerged overnight. Check for air-bubbles and the next morning check for water inside the floats. I solid; they can be re-used after cleaning with some water and soap.
For the other parts of the carb I would suggest sonic cleaning. If you dissassemble the carb yourself sonic cleaning isn't that expensive. Just make sure to dissassemble them completely!
Maybe the carbs are too far gone but if that's the case, you'll know they are and you'll never have to ask yourself: "Maybe I should have..."
If you manage to get the carbs back in good working condition, the satisfaction will be the nicest part of the whole project.
Another option is a rebuild kit for these carbs. Or buy all seals and jets seperately. Ask Google.
If you decide to go for replacing the carbs; make shure you get the right ones! The carbs are essentially the same but there may be other jets inside a 600cc carb then in a 900cc carb.
