Agreed I looked at the threads of the ones I got with my Grubbe gt5 engine and knew strait away that if after screwing it in as far as I could with my fingers then use a wrench to tighten it about a quarter turn it would probably strip it. Even after being carefull I noticed that I chewed a couple of the threads pulling the gear out. They are insainly fine threads.
Moral of my story -- Screw it in as far as you can finger tight without cross threading and then go 1 or 2% of a quarter turn with a wrench. and then insert the bolt that does actual pushing. (kinda weird why you call it a gear puller when you are actually pushing it out)
Or better yet if like me it is your first time doing this search YouTube for something like "pulling gears Motorized bicycle" -- YouTube has a wealth of knowledge if you can somehow separate the fact from fiction.