I have been having the same issue on my 94 NA. 4 or 5 different starters, the last one being a certified Nissan Re-man. Also tried 3 different flywheels, stock resurfaced, a no name aftermarket one, and the last is a Z1 lightened flywheel. I've just about given up on it and have since decided to just try a different transmission at this point. I have the 4th gear grind and sometimes 2nd. I bought a 98 Spec trans for my TT, so I'm taking the TT trans and putting it into my NA and then the TT will get the 98 spec. Obviously I will have to get a TT clutch and flywheel to fit properly. At that point hopefully all of the issues will then be resolved.