I've made a few of these threads before at different times in different forums, so this is a compilation and a place to brainstorm!
Earlier in the year I did a top end rebuild on my 1980 cb400n, camchain, piston rings, valves etc, however, I was still down on power after the work. It has the original exhaust system, and does not appear to be leaking.
I ordered two Keyster carb kits and they seemed to make a world of difference once installed, I could now sit at 120kph etc. From memory I did a carb balance after installing the carb kits. After several weeks commuting I decided to go on a proper ride (100kph vs 70-80kph on the commute), as soon as I was on the open road, my bike felt like it had reverted to its pre-carb refurbished ways, down on power throughout the rev range. I have not figured out why. I attempted to replace the coil to see if it would make a difference, it did not.
Carb balance?
Something inside gone askew?
Where would you look?
The only thing not to be changed in the carbs is the emulsion tubes, apparently the ones in the keystar kit are the wrong sort (according to my local mechanic).
