There are improvised methods that you can use to press on the pinion, since the end of the motor shaft at the endbell side is enclosed a hammer is out. You could use a vise as a gear press, but there needs to be a place for the end of the motor shaft to go or once it starts to clear the end of the pinion or the shaft is likely to bend. It is really a good idea to buy a good gear press and puller if you expect to do this very much.
See this article: https://drive.google.com/file/d/0BzLR42 ... sp=sharing
There is a list of tools at the end.