Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

As with all vacuum engines cleanliness in the cylinder is critical, they do need regular maintenance in this area but no lubrication.  It may be there is an oily residue in the cylinder from the manufacturing process which needs removal, solvent on a clean rag is best.
Flame size and height is critical and they are quite sensitive to draughts.  Hope this helps.

Dave