i riffed on mrpenn's "motorcycle scew on oil funnel" (https://www.thingiverse.com/thing:857406). i needed a smaller thread size for my bike (22.5mm dia.; thread pitch of 2mm). i built the funnel from scratch with shapes in tinkercad but borrowed mrpenn's idea of a breather (the tube along the side). probably would work on most hondas of that era. dunno.
i printed this upside down to avoids supports or rafts. took a little over 9 hours on a single extruder printer.