[rotorwrench]

A person can tune their own fuel system for best efficiency if they have an AF meter in the tail pipe. It may need smaller main jets if it's running rich as speed. Idle is controlled by the idle screws but a leak is definitely possible. Not all modern power valves fit older carburetors well if it has the vacuum type. I'm not well versed on the early 4100s but there are likely a few who are and may be of more help in this respect.