MS 171 leaking gas when put on its side

[GroundLoop]

Have a MS171 bought in 2012 and has never been serviced. It just started leaking gas when put on its side (see pic). I noticed it starts to leak when the fuel rises to a small black nipple (see pic with red circle). If you tilt the chainsaw to submerge the nipple it leaks. Stops once the nipple is exposed. Can anyone identify what this is? Is this difficult to fix?

 

[ILENGINE]

that is most likely the grommet for the fuel tank vent. connects to a 90 degree elbow and then a line to the vent that sides to the right upper corner of the carb connected to the area with the carb adjustment screws.