It might also be the gas tank breather tube. When it rains water gets sucked into the tip-over valve at the end of the breather hose, the gas tank develops a vacum and the carbs don't get gas. You can test this by unscrewing the gas cap after the bike stalls and if it starts right up, that is the problem. Solution is to remove the valve from the end of the breather line. However, if you do this and have a crash it is possible for gas to leak out of the breather and ignite from a spark and catch fire. I removed the breather valve after having this happen one too many times and am living with the potential fire risk. I guess I like to live dangerously.
