L293d problems?

Hey all, asked this in the #arduino channel on freenode but got no response, so I hope I'm posting this in the right place...

I'm using an arduino (nano) to control an l293d dual h bridge, controlling two motors (one on each side of an old RC car). It drives forwards, backward, left and right depending on what I tell it to do via serial. When I put it on the ground, there isn't enough (power?) to drive left or right (one motor forwards, the other backwards) the original car used a 6v battery pack, and i'm a 12v supply, so is my problem that I don't have enough current?

I don't know the motor's model as I can't see it printed on it, but it looks like this: http://www.maplin.co.uk/images/300/yg13p_new.jpg (just like any remote control motor I've seen)

Each motor is getting around 0.7a and 6v from the l293d chip, and I have no resistors anywhere in the circuit. Can anybody help?

Many thanks, S

edit: it's not a servo if anybody needs to know, it only has two wires. ordinary dc motor.

If you are using a 12V power supply and the motor only gets 6 Volt from the H bridge, then i think soemthing is wrong.

Are you sure yuo hooked things up in the right way ?