That plug is for an oil gallery in the upper front of the engine. Yes, if you opened while changing oil you would get 6 oz. of oil or so but no one ever opens it. I think you overheated your engine and that may have messed with the seal of this plug. Don't idle a bike for five minutes. There is no air flow and things get hot that normally do not. If you can't get out in the winter and bring up to operating temperature and the bike is on the maintenance charger, just look at it and think Spring. It is better off not running at all if the choices are idle in the garage or a short ride with out getting the oil hot for ten minutes to get the condensation out of it. And then there is the salt on the roads in the winter. I think you need a new crush washer under that plug and tighten it to the same spec as the drain plug. Good thing you came back, fire comes to mind.