Maybe steering head bearings came loose and must be a bit tightened? If I remeber right, when wheel off he ground, 1.2-2kg's force must be able to start move all when connected to center of one of the fork's top.
Stock shock's preload till maximum does not help- this old stock spring is too weak anyway...
Originally Posted by NorCalDave
I forgot to mention that I'm still running on the old, tired, stock shock and that the preload is pretty much set at maximum. I set it there before I took off on my trip through the Pacific Northwest last summer because of all the weight I was carrying. Never noticed the instability then - just seems to have become noticeable in the last few thousand miles