44.7mm carbs ?!? Dude , stock 750 carbs are what , 36mm ? And the 600 is 32 or 34 or something ? Those huge carbs would CHOKE a Katana !

I can see it maybe for a Kat 1100 set up for drag-racing use, where idle is set up around 4.5k and you spend almost all your time close to red-line.

For a typical street bike, a smaller carb opening induces more turbulance, which means the fuel vaporizes better and is more likely to give you a complete burn (resulting in better power utilization from the fuel that's there). The smaller opening also tends to richen up the torque band more lower-down (again, where typical street riders use it, rather than up at the very top of the rev-range).

Cheers,
=-= The CyberPoet

So then... would it be beneficial to put 600cc carbs on a 750cc Kat ('cause they have a smaller opening)?

I think that would be too much of a change, given the displacement of the engine. But going from a 36mm to a 35mm would be likely to improve it.

Realize, though, that you'd have to reduce the vacuum-levels at the airbox to match the change in carb body size (by reducing the filtration drag), plus redid all the jetting to compensate.

In general, you can think of it as a venturi -- the smaller the opening, the faster the air has to move through it, creating a higher vacuum at the carb openings and more turbulence... Unfortunately, it's not as simple as simply swapping carbs and calling it a day. But it is why many MC manufacturers bump back and forth between carb sizes (and why the 98+ Kat 600's use a smaller 32mm carb instead of the 33mm carb used on the 90-97 Kat 600's).

Cheers
=-= The CyberPoet