Hey Chris, I happened to stumble across your thread while seeking out info on the 1991 sm800 and took special joy and seeing what you've done here. The fact that you own two reinforces my particular love of this model and this particular paint job. I bought this exact bike new in 1991 from a shop in Racine, Wisconsin in the US and have never experienced a ride I've loved more than this exact bike. Mine was ridden for roughly 12 years until the components turned to dust and with head low she was retired to the garage for a new bike. After a decade plus had past I considered selling the frame and fork and actually listed it on Ebay for a day before I reconsidered and decided to refit with new parts. Everything except the frame, fork, headset, handlebars, and stem had to be replaced so it was incredible to see you come very close to catalog spec with your find. Mine unfortunately suffered damage to the dropout shortly after the rebuild. As it turned out it was fixable with a new hanger and only a bit of metal from the frame was lost(though horrible). When the bike was in the shop I began searching for a replacement frame though they are quite difficult to find if you need a specific year, size, and paint job. Low and behold I found another 1991 sm800, same size and paint, in the UK. So my original frame, though damaged and fitted with modern parts will rise from the ashes and I'll have another identical frameset to build up another. Two of same just like yourself(though yours are a bit more beautiful). Bike nut friends think my love for this ride is silly. Nothing can be that good they say but this bike is to me. It's the purest and most fun to ride of any bike I've ever owned even without the original components. To cut it short it was a great pleasure to find this post. Best to you, man.
I'm adding a pic of my sm800 but please don't slap me for the new parts.
http://postimg.org/image/trkq1y08b/