The gap between the pinion and spur gears need to be set correctly for the them to work efficiently and to prevent premature wear.  Too tight of a mesh can result in overheating and reduction of the vehicles overall speed due to the increased friction and/or premature bearing failure due to the increased load.  Too loose of a mesh will lead to premature gear failure as there won't be enough strength in the area of the teeth that are contacting each other.

Setting the proper mesh is most easily achieved by loosening the engine/motor and placing a piece of paper between the pinion and spur gears as shown in the image to the left.  Tighten the engine/ motor with the pinion gear against the spur and then tighten the mounting screws.  Rotate the gears to free the piece of paper.

NOTE:  Despite the fact that this method works with most cars, we cannot guarantee that it will work with all vehicles.  Due to different gear sizes, you may need to adjust the gear mesh by hand after trying this method.