Not uncommon with these, it is old and needs replacing ideally. I think member Craig managed to prolong the life of one of these motors (on a Beocenter 2200) by spraying it with WD40 or similar.
No one makes a replacement motor that I'm aware of but there are lots of Beograms which use the same one if you can find a broken one with a good motor.
Chris.
EDIT :-
As we speak THIS thread has been posted - the motors mentioned are identical to the one your Bg1800
The use of metaphors should be avoided like the plague. They're like a red rag to a bull to me.