You might want to check the "things to know" thread linked in my signature. It lists items to check when first purchasing a 40 year old machine.
This site has the factory service manual for your bike. You might want to download it.
Then, catch up all the maintenance. Looking at the parts fish on Partzilla.com, suggests your bike has points. That would be one of the first things I'd check. And while in there, make sure the mechanical spark advance mechanism moves smoothly.
Cleaning the carbs involves a lot more than just replacing old jets. In fact, there is no reason to replace jets, just clean them and reuse, assuming they are the proper size and type.