I love these big German twins and yours sounds and looks great.
It is too bad that it is too worn to run on steam.
I've had a couple of engines like that, in particular an Elektro.
Bad design and pot-metal engine/cylinder. I removed both the slide
valve and piston, filed grooves for a ring in each, and used twisted
Teflon tape for the rings. Works well so far and I'm working on
another. If it is easy to remove the pistons you might try this
tactic.
My Empire Playboy engine has a 'sloppy' motor that will not run until
I liberally coat the cylinder and piston with steam oil. It works well
after a bit of coaxing and makes me feel like the 'boss'! You could
try this angle. Certainly, easiest method to try
On the other hand, you have a nice working engine that sounds great.
Some would say "Why mess with success!". You only have to please
yourself.
Good Luck,
Wayne