I did this trip in 2008, it is amazing. Not for the riding experience but more for the places it takes you. Accommodation varied with great pools and hot spring tubs, it was a bit rough on the roads in some places and the height created problems with the Honda four hundred four that I hired in Chang Mai. I did it two up, no problem. If you are in the area go for it it is a great adventure.
I originally created this in my maps. Due to it being a 7 day tour I included fuel stops/food stops/ hospitals/ mechanics and places to see. Please email me for a link to it so that you can use this if you ever decide to go the views are spectacular