I think I may finally have figured out what’s wrong with my poor little loco. I had one final run with it this weekend (its 13th steaming as it happened) and after making sure there was plenty of oil in the cylinders it seemed to seal a lot better. It ran for a few minutes and even managed to run relatively slowly at times. Perhaps this is where I’ve gone wrong – washing the bits out of the cylinders with water left no oil on the surfaces to seal the pistons within the cylinders. We’ll see next week if I can repeat today’s run, but until then at least I have some cause for optimism.