for a short while running rich is easier on your engine than runniing lean. You will probably foul your spark plugs.
It sounds like you need to revisit your carbs and see if they are the problem....either that or a mouse nest in the air filters. You are running air filters aren't you?
If your cylinders were bored and honed they should have proper compression..........
Persistance usually overcomes problems. Basicly check everything, even wierd stuff. And keep track of what you checked and what the specifications and results were.