As some of you know I have had this on my mind for a while. I have a theory I would like to put out there and see what others think. Here is as simple and short as I can make it. The amount of fuel left in the lines past the petcock is so small the heat of the engine evaporates it when you stop the bike. This lets the float needles drop open a bit and the fuel level is left just about right at the needle valve opening area. As more fuel evaporates as the bike sits it leaves varnish on the needle valve(or float hinge) and sooner then later the valve will not seat well. I have tried to do some testing on how much fuel it takes to refill and re-seat the floats the next day after you stop from a normal temp ride. Funny it is just about how much fuel is left in the lines of the stock system. With the petcock valve working normal then no new fuel is allowed in and so you have air and fuel mixing at the needle valve and float hinge area. Most times this goes unnoticed until the petcock fails or the needle seals so bad that you notice rich running problems. Simple prevention might be as easy as turning the petcock to prime for a few seconds the next day after a ride if you think the bike is going to sit for a few days. Each time I do this you can hear the air rush into the tank as the bowls refill. I think once you fill the tubes and bowls it should sit better for a few weeks before enough fuel can evaporate to let the needles drop again. So what do you egg spurts think? Photos[/url]