oil leak from sprocket cover hole?

[jch]

I have had a slow oil leak since I bought my Girly late last year.  A couple of drips after riding, nothing major.  Last night I finally decided to find the cause.  I cleaned everything and then sprayed with white powder to find the source.  Turns out it is coming from inside one of the holes for the sprocket cover bolt.  See picture, everything else was clean and it was clear that the oil was originating from inside the hole.

I did a google search and found a couple of other instances, thought was that this hole was drilled too deep, seems strange but I guess I will insert some type of sealer to see if I can plug it.  Any other thoughts?

One other question, my sprockets look good but my chain needs replacing. Bike has 27K miles and the sprockets are suntour and chain is stamped with DID 50VM.  Can anyone tell me if the chain and sprockets are OEM.  Thx

[HockleyBoy]

Not sure about the sprockets but am pretty sure DID chains were not OEM fitment. Change the sprockets if you are changing the chain even if they look ok.