Hi, I've encountered several Steck Duo-Arts over the years with
Motoras. I have a friend that had two Stecks, with a Motoras in
each of them. Despite restoration of the player mechanism the
Motora ran hot and scarcely generated much above 22" wg vacuum.
Compared to the four-lobe mechanical pumps usually fitted they
were a waste of space. Perhaps they were just a poor man's option;
no doubt someone will comment on that speculation.
I actually made from new a four-lobe pump which I fitted in place of
one of the Motoras. As far as I know it still survives to this day.
So, Niels, if you can find a mechanical pump, put one in. It's not
original, but what the heck, at least it's less likely to catch fire
and that's got to be good for health and safety.