SCALEAUTO GEAR LASH ADJUSTMENT
Is the recommended method to adjust the lash by moving the motor in/out with the motor mount screws?
Yes. Use both motor mounts as needed to move the motor back and forth to get the mesh just right. You want to check the mesh all the way around the spur gear to make sure its set correctly. You also can check the spur gear to see how true it is by moving the pinion away from the spur, hold the chassis completely still and line up a piece of paper or something next to the spur gear and then slowly spin the spur around and check the run out of the spur gear. You can also use this method to check if its warped. Not all spur gears are created equally.
Also, other than replacing any spurs that are not oval or tacoed, are there any other best practices?
Just make sure the mesh is good all around the spur and not just in a couple of spots.