The original pieces, and the 3D-printed replacement:
(Attachment Link)
I've got the metal parts soaking in penetrating oil overnight; I'll clean them and try to reassemble tomorrow.
I realize I didn't explain about this very well... US SOHC forum member Smudgemo and his neighbor measured his broken switch housing and created a 3D CAD file for it, then submitted it to the printing firm, who will sell you one directly. Here's a post which covers the basics (it's part of a longer thread, but there's many missing photobucket pics throughout):
http://forums.sohc4.net/index.php/topic,163170.msg1931745.html#msg1931745
And, a link to his 10-minute Youtube video showing the process step-by-step:
https://youtu.be/Jirl6UqFSyE
So I'll post my experience here, but the links above provide great detail about this smart little product...
Job done. I didn't bother with pics, as there's plenty on the linked thread, and the video speaks for itself.
My switch works again - at least it passes all the VOM tests. I can recommend this thing for the US spec CB400F switch... with very minor reservations: the guy makes it look very easy on the video, and it wasn't so easy when I did it - I believe that there may be some "error" in the 3D print process that was used to make this switch body, and that maybe the plastic ended up a little too... "thick?"... in all dimensions - if such a thing is possible? The openings were all just a hair too small, so the little tabs on the switch parts didn't seat easily - although they did eventually. The start switch button bound slightly in it's u-shaped slot; I had to scrape some of the plastic away until it moved freely. And once I got the parts situated inside the switch body, they flexed it so it ended up being a bit too thick to fit into the handlebar housing. I ended up using a sharp utility knife blade as a scraper to shave a bit off the sides until it fit easily. I've communicated my experience to the designer, to see if he has any thoughts. In his video, everything dropped right into place with minimal bother...
If I did it again, I'd test fit the empty shell in the handlebar housing, and maybe hit it with some sandpaper before installing the switch guts. Still and overall, though, I'd call it a success! $15 (in the US, anyway) to keep my otherwise original and working handlebar housing intact. 4.5 out of 5 stars.
I'll still consider changing over to switchable headlights, however...
