As I've said before: 1) it's never happened to my F2 and 2) I'm not sure if the carbs have coolant heating tubes in them...but if they do and they've been disconnected turned off or restricted the carbs could ice despite the warm climate; my truck used to do it all the time. If the bike is warm and fails, if you wait a few minuites for the engine heat to move into the cabs warming them and melting the ice, then it would start right up and run fine until the next time. As I've said I'm uncertain of the above points but I am sure that it is at least possible, so i would open the fuel cap and try or wait for heat, as I said previously.