Hi – thanks for confirming that the bolt (12m head/ 8mm shaft diam.) is right hand thread – at least I haven’t been tightening it! I cannot remove it without the risk of it shearing. I have found that the 2 little lobes on the advance/ retard fly-weights have sheared – these locate in the slots behind the cam and that’s why the cam rotated freely. I have managed to remove the springs and remove the 2 fly-weights and fit replacements without undoing the offending bolt. But … I think the cam is now 180 degrees out and the fly-weights cannot now be removed (the old ones could be removed because the little lobes were sheared). So now I am stuck! I was wondering if I swapped the plug leads around if it would compensate?