I suspected my squared/worn rear tire (new one on order), but this wasn't quite what I'd expect from this problem.
I decided to check the steering head bearings. Fine, but... The steering damper was acting weird. I usually tighten it until the drag is barely perceptible.
What was happening was that no matter how much (within reason) I tightened it, there was no dampening on center, and then the aforementioned "thunk" (quite soft) followed by damping. Hmmm...
I'd never paid any mechanical attention to the damper before, so I took a good look at the unit (under the triple clamp) while I moved the bars. In the (undesired) no-damp range of motion, the lower plate (the one clipped to the lower triple clamp) moved back and forth. Then the "thunk", no motion, and damping.
A quick look in the service manual made me suspect that something was wrong with the "Damper rod rubber ring - /5 only" The plate that attached to the frame of the bike appeared to be centered by a large boss on the lower triple clamp, but the plate that attached to the lower triple clamp appeared to be centered primarily by the damper screw (the one that attaches to the knob). This screw is centered by its rubber ring.
Last night I took the damper apart. I couldn't find anything resembling this ring in there at all. A few pieces of "dirt", but not enough to make up the part in the pictures. I wonder how it ever worked well...
Well, I made a new rubber ring (am I cheap or what?) and installed it.
I cleaned the friction plates and painted them (except the friction areas).
Since there was some apparently graphite-based spooge on the plates, I put a _very_ small amount of "never-seize" on the plates. The Haynes manual is completely silent about reassemble/lubrication of the damper. They just say, "It is highly unlikely that friction type dampers will ever require attention". Two things come to mind: -Maybe I should buy a lottery ticket. -Why did they stop using frictional dampers if this is the case...
I put it all back together and tried it. Smooth. Better than it's ever been. The "never-seize" seems to have been a good idea. The damping is easily adjustable between none and "How can you ride that?"
Jim Buchanan firstname.lastname@example.org email@example.com ==========http://www.holli.com/personal/jbuchana/jims_page.html=========== "When from my mither's womb I fell, Thou might hae plung'd me deep in Hell, To gnash my gooms, and weep and wail In burning lakes, Whare damned devils roar and yell, Chain'd to their stakes." -Robert Burn