[Nonfractal]

I have a genuine Ninco tool that I'm ok with.

Some problems:
Not intuitive. I've seen novice racers use this upside down and destroy their motor. 
Alignment of the shaft to the locator hole is not easy. 
(Damage the commutator if you are heavy handed)
Close-fitting pinions are hard to remove because the claw part if the tool can't get behind the pinion.
More often than not, the motor will have to come out if the pod to get to the pinion because the tool is:
- Too narrow overall to go around the pod. 
- Too wide at the puller end to get past the pod and behind the pinion.

The Ninco tool will chop into the end-bell bearing cover (NSR long can) so requires a file or plate to protect the can while using the tool.
There is no way to easily set the tool to push a new pinion to the same position as the one you just removed.

I've often thought that the pull and push should be separate tools which would make it easier to use each. 
Threaded tools are just soooooo slooooow!  OK if you are not in a hurry but if you are doing an enduro, every wasted second hurts.

I've had several attempts at designing a new tool but really have not cracked that nut yet.
Inspiration is being taken from mastic guns and wine bottle cork pullers.

Alan W