That nut had not been touched in 5 years. Den, the valve clearances have rarely needed adjustment on this engine. The parts dont wear much with the better oils in use now.
I did check them but only after checking a dozen other things Den. Gap was over half an inch with no pushrod in place !
Its made a mess of the adjuster and the nut will never fit on anything ever again. Leaving it for the rest of the day as after a few hours tinkering, i get a lot more hand tremors and i know its time to stop.
Since getting the shakes, jobs i used to do easily take about 4 times as long.
Good thing is its not getting worse and its not Parkinsons. I can keep my licence a bit longer.