My America experienced the same problem in an extremly heavy downpour, it isn't the kickstand switch, because I took mine of the day I bought the bike because I was told rain affected it. I'm 95% sure it is the carby breathers getting doused in water from the front wheel, try it for yourself put your finger on the carby breather and the bike experiences the same symtoms. I have cut the breather a little bit shorter and on a very acute angle. We always used to cut the carby breathers back to within 2 inches from the carby on our enduro bikes to stop them from stopping when going through creeks and rivers. Unfortunately it hasn't rained hard enough lately to test my remedy. Best Of Luck.
