Program only runs sporadically

No the zeroing code was not supposed to be commented out.

The library is here: https://github.com/clearwater/SwitecX25

Annoying thing is that it worked on an arduino uno shield for testing but having rigged the actual board up and the motor in it's housing (Motorbike speedo) it's all going nuts.

I assume you have the correct sort of motor that the library is intended for.

I know nothing about those motors or the Library (though they seem interesting).

If the motor works when it is on the kitchen table but not when it is in the motor bike I would suspect interference from the 'bike electrical circuits.

...R

All we did was flip the ignition, the motor moved smothly one way then the other. The purpose of the zero function is to run the motor backwards full scale so that it hits the lower stop point so that the the motor is then indexed for any further movements