Zanussi TC481W replaced belt only starts in one direction?

My drier stopped working, took the back off, broken drive belt, replaced it as per the info on here.

When the drier tries to spin anticlockwise the motor starts up fine and spins the drum ok, when it tries to start in the other direction the motor tries to start but just makes a funny sound. If you give the pulley a twist in the right direction then it runs ok, its almost as though the motor doesn't have enough torque to start itself in one direction.

Any ideas?