The stub on the new motor was retained by a rivet, once that was drilled out it came out easily. The stub on the motor in situ was stuck so I took the barrel off. The new motor fitted easily and is now sitting in the frame. A pity the otherwise excellent Mr Kelly (technicalities) didn’t mention the stub in his article. So thanks Lewis for getting me out of a jam.
Dave, aren’t you referring to the 3-speed motors? My 2speed one lifts in and sits on the bottom frame rails rather than between them.