Turns out the rubber bumpstop was missing both of its tits, one of which had been replaced by a small bolt. The bolt looked like it hadn't had a nut on it for some time so I surmise that there was a remaining tit that gave up the ghost somewhere along the road, allowing the bumpstop to fall to the ground when the bike went on the centrestand to be filled. When I remounted it, knowing no better, I used the wrong hole in the mounting bracket so strangely enough nothing lined up like it should....
Thanks again for the quick response, Gryph.
Back to your regular programming!
Martin the other
in the too hot to work outside Riverina.