The valves were running totally un-lubricated and had worn badly.   The valve face had rusted and become scored.  The mechanical lubricator was adding oil to the forward end of the cylinders, completely by-passing the steam chest.   The engine has Joy valve gear and the die-blocks were very loose in their slides.  The free play on the valve was almost equal to the full opening of the steam port!  Clearly this would do nothing to promote reliable and smooth running.
The pistons, which were a loose fit in the bores, had been assembled without piston rings.  Leather or similar fibrous 'seals' had been used in place of the rings and these had deteriorated.  When the engine was stripped they were found as an untidy and soggy mess.  This, coupled with the shortcomings in lubrication, resulted in the cylinder bores being badly pitted and corroded.
		The solution was to re-bore the cylinders, make new pistons and fit proper piston rings.  In addition, the valve face was skimmed and the valves lapped in.  In addition the lubrication system was modified so that the steam oil is injected into the live steam feed before the steam chest.   In this photo the 2nd bore is receiving attention, the far one and valve face have been machined.