Provided you are using the 5mm tip on motors etc I use 400degC for motors.
Should only take a couple of seconds for a motor wire (quick enough for you to hold the wire with your hand, if you're burning yourself you've had it on too long).
Typically use 350degC with the 1.2mm tip for smaller jobs.
Xray T4'16, T4'14 (Wet Car)
Xray X12 2016
wlrc.co.uk (West London Racing Centre)