just close it a bit, what size is the orifice? if i remember a 1/16" is the norm for a non- adjustable. i thinks thats the size i drilled my homemade one to

 

You just need a simple oil restrictor fitting, like this:



For jurnal bearing the hole size is .063 like mine on the picture and for small BB is .032.
and use thiker oil like 5-30,40 or 50, but not syntetic because its gonna make it worth.