A sample from the products for the Lower Crankcase include: Bolt,flange,6x80, Seat,oil Spring, Element,filter, Oil Seal12.5x25x8.
This schematic depicts all components used in the Cb400nc 1983 (d) Netherlands Lower Crankcase partslist.
In this schematic the "Bolt,flange, 6x32" is used most often.