[Cory]

Ive had no problems with this method of pressing on the pinions.

Place the gear flat on the bottom of your arbor press (Note, this is with a lever actuated press with very little slop--not a hydraulic press, some of which have a LOT of slop).

Place the motor shaft down on top of the gear, with the shaft on top of the hole in the gear. Level the motor roughly by eye. very gently and slowly apply pressure with the arbor press to begin pressing the gear onto the shaft. You may have to bend the tabs for the leads down a slight bit to make sure you're pushing only on the shaft where it exits the rear bearing.

Every few seconds remove pressure and watch for the motor to "spring" back. If it moves you're not aligned straight. Move the motor/gear under the center of the ram until you no longer see any spring.

Continue pressing and checking until the gear is where you need it.

The above method should come out centered, as you're relying on the bore of the gear being perpendicular to the face of the gear, and you're referencing the face of the gear off a flat surface.

For anyone who hasn't done this often, these are a VERY tight fit. You will in all likelihood feel like you are going to break the motor while doing this. Just go slow and make sure you have everything perpendicular and you should be fine.