HELP! Model G Oil Leak from under the Magneto. Why?

[Hobbes64]

Hi, I have a Model G 1949 that I have been working on and after a ride yesterday oil started to leak from a hole behind the timing cover, it's in the crankcase just below the magneto stand, it looks like a previous owner put a wooden dowel in there, why would oil come out of this hole. See photos. Any help appreciated.

[ERC]

I could be wrong but there is a passage in that area to return oil to the reservoir. Maybe somebody drilled a hole in there to see if oil is circulating properly. Then put dowel in there to block leakage.    ERC

[barenekd]

It was probably drilled through for the initial manufacturing and plugged with a metal plug, which eventually fell out. It looks like a short rivet and some JB Weld would fix it.
Bare

[ERC]

I think Bare is right the only way to know for sure is to send the pictures to Hitchcocks, they would know.   ERC

[Arizoni]

I'm pretty sure bare is right.

It looks like the site for a tapered pin expansion plug.
Often it is necessary to drill holes for oil or air to get it from one place to another.  The only way to make these transfer holes is to drill them from the outside of the housing but this leaves the hole where the drill bit entered the case.
These small expansion plugs are then inserted into the mouth of the hole and usually expanded with a tapered internal pin.

For a look at these pins follow this link:
http://www.leeimh.com/metal/betaplug-expansion-plugs/betaplug-expansion-plugs.htm

As bare suggested, degreasing the mouth of the hole and epoxying in a metal plug or rivet that fits will fix the problem.