[benl]

Hi,
Not sure if this will be any help at all but a couple of points to watch out for.
Have you tinned the tip of your soldering iron (covered it in solder) and is it clean.
You also need to tin the ends of the wires and the contact points on the motor. This should help to get everything flowing.
Is your soldering iron a high enough wattage?
You need to heating either the wire or the contact point and adding the solder onto these rather than directly onto the iron.
Also leaded solder is best although I just use the cheap stuff sold in most hardware shops.
Sorry if this is all old news to you I'm by no means the best solderer so hopefully some others can give you some more advice!
Thanks
Ben