Fixed!
Thank very much for your help.
The breather assembly being installed upside down seems to have been the culprit!
Such a simple error but so much anguish! A lesson well learned!
The old woodworking adage of "Measure twice, cut once" springs to mind.
The previous owner, a mechanical novice like me, managed to install a conrod, install a set of rings, do a valve grind and put the engine back together but all this good work was brought undone by a simple error.
Thanks again for your help.
Rob.
