Harley 4 Speed Leak Fix

This fella I know sent me this print on how to machine an o-ring groove in the ID of the spacer (the spacer that's driven by the small "L" key the main seal rides on)
The part number of the Viton O-Ring is available from McMaster-Carr Supply.  You can get the actual dimensions of the o-ring in the catalog.  The spacer is probably pretty hard, so you need a good, solid, rigid lathe - and a qualified machinist.