When I am trying to find a water caused shutdown , I spray the entire bike with a hose , this works most of the time and the spark plug boot / wire is the most common problem , but I have had a problem with my 450 where hosing it would not make it shut down , it was a process of elimination with changing parts , on that bike it was the coil --------- use the water line of where it shuts down as a reference to where the problem might be