For the bevel gear, you will want to maximize contact with the spur gear teeth and have proper engagement with the pinion gear (motor gear).

The simple way of achieving this is too shim the bevel slightly higher then center and to give it a little more slop then the other gear. Just make sure the spur gear is making full contact when the bevel is pushed up and not binding when it is pushed down.

There is a more advanced technique for shimming the bevel gear which will be mentioned in the next step.