Slightly odd question.
I've finished a Stuart No8 and have run it on air for a couple of hours. All the mechanicals now turn over really nicely, no sticking or play and the engine will run slowly on a few pounds of air pressure.
However the piston is still 'tight' in the cylinder. It runs on a couple of cast iron rings which simply seem to be 'gripping' the bore pretty well.
I've been sending plenty of oil down with the air (in fact the entire engine has practically been sat in an oil bath).
(I've also whizzed the end cover off and the bore is fairly shiny where the piston has been travelling).
I've seen a number of engines that will spin on slightly when the flywheel is spun, that's the sort of free running feel I'm after.
Any hints or tips? (It probably doesn't really matter as the engine will simply live in a glass cabinet, but I feel it should feel 'free' before I can consider it finished...)