Ok I am a little confused now...based on this comment I got a 88T 64 pitch spur and a 43T 64 pitch. They will not mesh together..... so what size pinion and spur actually work together ? At least not with 3 motor mounting screws... two screws it will work
Just keep going up from there. Try a 90/45 and 92/46 and so on, eventually you find the sweet spot for gearing. It's going to vary with what you are running. Like I said I am running a 94/48 and I can fine tune with the same spur and switch down to a 47 or 48 pinon or go up all the way to a 55tooth pinion as well.