I have a lightning 50 I think it is eton brand. I just had the side case off to fix a small crack in the case. Was leaking a small amount of gear oil. I patched it up and put the cover on and all seemed to be good until I started riding it. When I returned from the test ride there was gear oil seeping out of the hole pictures on the right side on the gear case. I'm not sure what this hole does. Is it possibly an overflow? I may have put a bit too much gear oil in it. What do you guys think?

 

Welcome to the forums.
No pic so I cannot say for sure, but there is a hole that usually has a bolt in it. Usually filled till the oil comes out that hole.
I suggest finding a parts fiche somewhere.

 

https://imgur.com/a/vSjdxwg

Pic here

 

OK, how about a pic a lil farther away so I can see where that hole sits. THX.

 

I ended up just finding a random bolt and cramming it in. Looks like that took care of it.