saw this on one of HD-related FB pages. Why drill the clutch hub shell with extra holes?

 

I assume to get more oil on the clutch plates, and to me that's a very bad idea. The early four speed clutch is really a dry clutch. What oil that's in there is just enough to lube the primary chain. Dropping more oil on the plates may cause clutch plate glazing.

 

I could see it on a belt drive. Cooling for the plates .Lighten up the basket. Those holes need to be drilled kind of precisely to keep the balance.

 

Possibly to lighten the shell, and the holes might also help to sling oil away from the plates while running provided its not over full. Pure speculation though.