Here is what I did for my K-line Torpedo:
Take the smoke unit to a gun store and by a bire swap that is a tight force fit. Get some polishing roug. chuck the swap up in a power drill, load the swap up with some rought then use the drill and swap to polish the interior odf the cylinder. Once the cylinder is polished, the piston by chuck it in the drill and hand hold the swap while spinning the piston. Once that is done, cjeck the piston for a groove cut in its circumfrance, it is for an O-ring. Refresh the O-ring with the porper replacement from Lionel. Once all that is done, lube the pison with a very light coat of vasoline and reassemble. Should work as new.
I have a lathe so the piston polishing did not require an extra set of hands.
