John Deere CS 81 oil leak

[Timberguytim]

Hi, this is an Italian made saw, as you probably know, an 81cc Olympyc. 
Oil been leaking since I purchased it used, but mint last year. Seems a chain oil reservoir vent hole just underneath the coil mounting post....or it it a flaw in the casting? Help!!! Pretty messy, thats probably why the guy sold it? Thanks, Timberguytim.