Older style e50 case. I’ve come across a few of these over the years. Cut and pasted from a previous thread here regarding the extra “drain” hole.
“My Maxi manual has instructions on how to store your moped over the winter. The manual is in Danish but this bolt is called a "ventilation screw". I´ll try and translate this in English.
Unscrew the spark plug, carburetor and intake from the engine and bring the piston to TDC. Pour 30 ml of engine oil trough the cylinder intake hole and turn the engine/pedals few times. Screw the spark plug, intake and carburetor back on.
When the moped is going to be used again, after winter, it reads.
Unscrew the spark plug. Unscrew the "ventilation screw" and turn the engine/pedals with the petcock closed. Oil should drain out this hole. Screw the spark plug and the ventilation screw back on, open the petcock and start the engine.”