Although I don't have an answer I do know the question on everyone's mind will be what is the manufacturer and what is part number? Not all motors are the same.
AC Induction motor:
Some are PSC, Permanent start cap motors, in this case, the windings are equal and the cap is swapped to the other winding to reverse, can be done with simple SPDT SW.
In general, one winding has the cap in series, start winding, the other winding is across the supply, run winding
maxhadroom. i understand that, but why are there 4 terminals, what's inside and how is it connected? i would far prefer a 2 terminal one, but none obvious on ebay, so why made that way?
If this is in fact a 4 terminal cap and there is no connections between any pair, then it could be a dual capacity unit?
What is on the label, show a pic.