[DanEC]

I also second float level and/or bad needle/seat. I will add that it also may be fuel boiling over in the float bowl when the engine is shut down. Strange it would suddenly start doing so unless the engine is running hotter than it used to or the fuel line has been re-routed or something. If you have room you might install an insulated spacer under the carbs. Also, check coolant temperature when hot. It could also be a re-formulation of ethanal in your local fuel that pushed things over the edge.