Ok, since this comes up ever so often and Armi is struggling with it, here we go.
Your float system does several things:
First and foremost, and having nothing to do with adjusting anything, it serves as your final safety valve to control and stop fuel flow into your carbs. Our bikes do not have a manual petcock, and therefore no "OFF" position, but rather opened and closed via vacuum provided via tubing from an intake manifold. In other words, your motor must be running, to provide vacuum (unless your petcock is faulty) to flow fuel to the carbs. Should it fail, your float system should shut fuel flow off via the needle and seat. Should your needle and seat fail, you will likely overflow the float bowls on the lower (leftmost carbs) if it sits on a sidestand, it will drain down the intakes and fill the combustion chambers, possibly leading to hydrolock on startup. At the very least it will drain past the rings and contaminate your engine oil, possibly causing lower end bearing damage.
Secondly, and for the purpose of this post, float height can contribute to low rpm jetting maladies (full throttle and steady state cruise), engine run-on in hard braking, and minor irritability.
The floats are sensitive to impact. therefore....if you trailer your bike long distances or drop a carbed bike....check your float height.
If you have an engine loading up and not idling down under hard braking, try lowering float height.
If your bike runs clean at low rpm when cold but not once warmed up, and testing shows that your pilot jet is correct, rather than go back down to a smaller pilot jet....lower your fuel level 1mm (raise float level)
Running rich at part throttle is usually a symptom of too high a fuel level.
Remember: Lowering your float height raises the floats which raises the level of fuel in the bowls. Raising the float height lowers the level of fuel in the bowls.
So, the obvious: remove seat, raise tank, remove air box, cables, remove and drain carbs.
Remove float bowl covers
Invert your carbs so that you may better manipulate them as a vertical column and control the compression of the needle and seat.
Here is the trick: slowly tilt the carbs so that the tang on the float drops the needle all the way down into the seat, BUT DOES NOT COMPRESS THE NEEDLE. Verify by depressing float with your finger and watching it rebound!
Now, measure from gasket mating surface to top of float....the standard setting for both 600 and 750's is 8mm.
Use a pick or small screwdriver to bend the tang, which in turn, raised and lowers the floats.
Make sure that in doing so, you do do pry the tang out of the arms of the needle that keep the two engaged.
I use a rather expensive Kowa Seiki tool that I have had for 16? years
You can use vernier calipers, rulers, or even make a plastic gauge......
What did I leave out?