Suspension stem advice

[Mr. Zero]

is that made by allsop looks like the softride stems i have?

that was my first thought, but there's no name on it. It could well be - where were they made?

Indeed this one has no damping, but I'm curious to try it anyway

Softride (Allsop) is in fact in Bellingham, Washington and it does appear that what you have there is an early aluminum model Softride Suspension stem. Later aluminum models had the top link milled out. If you're interested, the last time I checked Softride still produced threadless clamps that could be swapped onto the stem in the event you would like to go with a threadless setup instead.

http://www.bikepro.com/products/stems/soft.shtml

Sounds like jango has you sorted with the shim, but the piece that you need is the bit on the right in the image below:

 

[sfcyclotourist]

That's an early model Allsop Softride "Frankenstem". I had one many years ago which I bought used. There was a recall on those as the top "dogbone" welded piece tended to crack. Allsop sold me a replacement stem -- the new silver version with the CNC-machined linkage pieces -- along with the return of my old stem, for $100.

The early black stems used brass pivot bushings which wore out rather quickly. The silver models use plastic bushings that last a bit longer. When the bushings wear, you get up/down play in the ends of your handlebars, unfortunately. As someone previously wrote, these things had no damping, unless you got the extremely rare add-on damper unit:

I have some additional old info on these stems here.