I was told once to think of an engine as an air pump. Air is sucked in and expelled. The amount of air sucked in on each stroke is dependent on the volume swept by the piston, the design of the cylinder head, the profile of the camshaft, and the design of the exhaust.

To get adequate vapourisation of the fuel from the carburettors the air must be speeded up in the carb venturi. This is why the venturi is known as the choke. By squeezing the air into a narrower channel it must speed up, a bit like putting your finger over the end of a hose pipe. Generally the carbs fitted as standard are matched to the engine so that happens optimally. If you fit bigger carbs without altering the cylinder head, and/or camshaft, the air won't speed up as much, fuel vapourisation will be poorer, and the engine will be less efficient. It may produce less power than standard and it will almost certainly waste more fuel.

It is generally incorrect to think that bigger carbs mean more power. Here endeth the first lesson.