a bike will start without the battery but the battery cables, positive and negative can't be left hanging without a connection..
on my honda C70 runs without a battery but there's no lights.. no starter motor... etc.
With a battery, the positive battery cable connection pathway is into the positive pole of the battery.... through the battery's plates... out through the negative pole, and finally grounded to the frame.
So, without a battery, the positive cable path is simply to be directly connected to the frame (a ground) to complete the circuit. Then it starts and runs.