DC Motor consuming too much current
So without any more information this is what I would suggest to check.


Check the voltage on the motor leads while it is in the toy as well as your current application. Just because something has a 12v battery doesn't mean that the motor runs on 12v, there could be some voltage regulator hidden away.
Make sure the motor can spin freely. If something is binding up the motor or a magnet inside has come lose it can create a very large load on the motor which will drastically increase its current consumption. It should spin without any clicking or grinding.


Some questions:


Can you see a model number or any identifying marks on the motor, you may be able to look up a datasheet to confirm the voltage it needs. 
In your new system, is the motor under load or spinning freely? As I said earlier, the more stress you put on the motor the more current it will draw.