How to set float height

Setting float height can be kind of intimidating for some people, but it's not hard to get it right. The trick is to hold the carbs as they would normally be positioned, then slowly tilt them until the float just "flops" down. The height should be measured at that exact spot. You may have to do it a couple of times to get that "sweet spot", which should be at the point where the carbs are almost horizontal. (This pic might be a little misleading in that you won't have the carbs this far over, but maybe closer to 45 degrees.)
The floats are connected to a valve that feeds gas to the bowls. Inside that valve is a spring. You want to measure with the little metal tang touching the valve, but not compressing the spring. Measure the distance from the gasket surface to the highest part of the float.
The factory shop manual lists the recommended float height at 13.5 - 15.5mm. My bike likes the floats at about 15.5-16mm. Normally, if you are within the factory spec, you'll be fine.

If you find that your floats are not within spec or you're experiencing a float height related problem, the height is altered by bending the metal tab. Go easy here. A little bit goes a long way. You don't have to remove the float assembly to alter the height, I just did that in this picture for the sake of clarity.
When you're measuring the height, be sure that the float assembly is "seated" in the carb body. If you hold down the "frame" of the assembly with your finger, you will get a more accurate measurement. Be careful that you don't push down too hard and cause the assembly to be distorted, though.

Improper float height can cause a number of problems, primarily in the lower midrange, say 2-4K RPM. Bear in mind that increasing the float height measurement will actually lower the fuel level in the bowl and decreasing the float height number will increase the fuel level in the bowl. Remember, the floats are mounted upside down in the carb.

Lower float height / increase the measurement to counter a rich condition.

Raise float height / decrease the measurement to counter a lean condition.

If you think you have a problem that appears to be carb related, go to the Factory Pro tuning page. This page is the absolute best carb tuning resource I have found and it will save you hours of time and frustration.