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.

Cheers,
Paul Camps