Unipolar Stepper to Bipolar

Hello all I am having trouble running my unipolar 6 wire stepper as a bipolar with a big easy.

I have tested my code and it works with my bipolar 4 wire motor so I am looking to connect up my 6 wire, higher power motor in a bipolar orientation.

I have a sst55d2c020
A quick search on the net pulls up the data sheet at
http://www.aet.calu.edu/ftp/cet/335/SKCmotors.pdf

I have followed the data sheet hooking up the brown/orange into A, A- and Red/Yellow int B,B- leaving the center taps unconnected to anything.

This results in the motor making noise with a slight vibration. Using my code I can change the delay for the pulses with the serial. When I tell the motor to stall or stop it will not vibrate or make noise. If I set the delay to 1000 the motor vibrates lightly when you touch it. So the code is sending the commands correctly and the servo is getting the commands but is not moving. When playing with the motor leads thinking I had the connections wrong I unplugged the A- connection and the motor started to spin. I am not sure why it spun with three connections but haven't been able to repeat it since.
If anyone has a clue I'd appreciate it.

Sounds like you don't have it wired properly. Are you sure you have correctly identified the centre connections? Use a multimeter to be certain.

And are you sure they are not connected to anything, not even to themselves?

...R
Stepper Motor Basics
Simple Stepper Code