This video demonstrates how to remove a pinion without using an actual pinion puller. The motor in this case is a Scorpion 2221-6 with a Rhino hardened steel pinion. When I installed this pinion, I used medium strength thread lock on the shaft as well as on the grub screw. I did this so I wouldn’t have to worry about the pinion slipping during use. The drawback to this is that pinion removal will be extremely difficult to accomplish by hand.
What I did after removing the grub screw was use heat from a soldering iron to break the thread lock bond. After that I used needle nose pliers to get the pinion moving up the shaft slightly. As the gap between the pinion and the motor got larger, I filled the gap using hex drivers. This is done in order to provide a surface other than the motor to pry against, as well as to avoid any side loads on the motor shaft that would be made by prying at an angle.
Using larger tools as the pinion gets further up the shaft, eventually the pinion will reach the end where it will simply pop off or can be pulled off by hand. Using great care, this method is safe and will result in minimal or no damage to any components of the motor or the pinion.