It is more than likely to be the other way round - the motor being too much for the battery. -

The chances are is that the battery you are using has a C rating that is too low for the amount of power you are trying to suck out of it, which is probably why it is getting too warm.
If this is the case, then your battery won't last very long, and will damage it permanantly.

Example.
All lipo batteries have a C rating
If the battery your using has a Rating of say, 10C then the maximum you can draw from it constantly is 9 amps because your battery is 900mah (10C = 10X 900 = 9000 mah = 9Amps) (1C = 900mah = 0.9 amps)

If your motor is taking say 15 or 20 amps form the battery, then it is obvously overloading it.
I can't say what yours will take, as I don't know much about the brushless type of motor that you are using, so you will only know by using a proper flight test meter or amp / watt meter.

If this is the case, then you need to be using a battery with either a higher capacity, like 1800mah, 2000mah, or a battery with a higher C rating, or even both higher caoacity and higher C rating. - the more the merrier.
Newer more expesive types can take 20C, which in your case for a 900 mah pack would happily take a pull of 18 amps.
The more discharge rate it can take the better as it won't strain the battery so much like my set up-

I have an electric piper cub, with a 2 cell lipo of 1800mah in size with a discharge rate of 12C which allows me 21.6 amps to be pulled from it constantly.
The motor in it only pulls 8.6 amps though, so there is plenty of leaway, as there is room for me to be able to pull more than twice of what I am using at the moment, this will prolong the batteries life, as your not killing it just for normal use.

It lasts for 20 minutes of flight flat out throughout, and stays as cool at the end of the flight as it was when it was put in at the beggining of the flight.


Hope this helps you.

Regards, Craig.