TOPIC:

After months of successful carburetor function I go to ride my bike after letting it set for 3 weeks with the petcock off. I'm setting at a red light and I look down to see my carbs overflowing with the bike running. I'm ready to sell this high maintenance beast.

rdbhere2, I can understand your angst. Two weeks ago this very situation occurred to myself after I had ridden 40 minutes uneventfully to visit a friend. When I went to leave we could both smell fuel and same as you - that wet spot under the bike. I was glad I had installed the over-flows. Bike started easily and got me home. The clear over-flow tubing indicated it was the 5 & 6 carb. I got the carb-set to the bench, removed that bowl, supplied fuel and lifted the float manually and confirmed the float needle wasn't shutting-off. Pulled the float and needle and found a piece of foreign material stuck in the valve-seat. Removed it and all was good. The culprit was very small. With a jewelers-loup I realized where it had come from. It was a "tiny" sliver of fuel-line, down-stream of the fuel filter. It had remained attached for a couple of years since converting to a dual fuel-line, until the event. As with you, I had not done any recent carb work and all had been dry. It's the "time-frame" that can be misleading.
This can happen to anyone at anytime. (Apparently !) Although in my case the piece-o-crap was down stream of the fuel filter it none-the-less exemplifies the need to ensure a good quality filter is installed. More specifically: It also shows that a high degree of attention be paid to how you do something as apparently simple as cutting the fuel-line. Most fuel-line material has a woven re-enforcement layered into it. Depending on how it is cut, some "fuzz" can remain which can come free at any time. Once any foreign material gets to the float needle-valve - your done !

Strange thing happened the day after my bike carbs flooded several times WHILE riding. I rode all day and not once did the carbs flood.It was a hot day and a couple times I forgot to turn the gas tank valve off and the bike carbs NEVER flooded. Very strange.
These bikes definitely do not like sitting. I knew it was carb float valve related. These brass floats are awesome.