I cannot remember what kind of motor i recorded, as i did this recording in 2013. Its recorded with a h4n somewhere in the city centre of london (uk) and i used it previously for car sounds.
This sounds like an old mississauga transit (mi-way) bus engine starting, running for a short time, then slowing down. The sound was made by simply playing the sound of air raid siren backwards.
Tried to emulate sound of a large motor starting. This sound is actually from an air raid siren. Reminds me of some transit bus but also sounds like some electric motor.