Take a look at the cb 650 stem, is there a beveled ring ? is so remove it for more threads at the top.
If what you say is accurate it came off a frame with stock bearings, all the little balls right?
the neck side race for the bottom ball bearings slides down the stem from the top,
and should come off the same way.
What do you do when you have a billion dollar idea but no money to build the prototype?
The One And Only Gypsy Weeble