Refer NSW RTA ‘Towing Trailers’ booklet.

Maximum Towing Mass (Loaded trailer weight).  Must not be more than the unladen mass of the towing vehicle.  In my case, this is 243kg.  That’s PRETTY. DARNED. HEAVY.   Of course, if the vehicle manufacturer has specified the towing mass, then that would be the maximum (up to the 750kg trailer limit). But most motorcycle manufacturers (even BMW!) don’t actually specify a maximum towing mass…