1995 Toyota Camry Engine won't turn over

I have a rather difficult problem. I just replaced all piston rings. I couldn't loosen the crank bolt and wedged a breaker bar against the ground and tapped the starter. Bolt came out no problem. Accidental tapped again and heard the starter spinning up but not engaging. Proceeded to take engine appart and replace rings. Got everything put back together starter still doing the same thing. Took starter apart, but didn't see any damage. Charged battery (thought perhaps there wasn't enough amperage to turn engine over). Still same problem. Got a remanufactured starter at Pep Boys. Still same problem. I hear the starter spinning, and the it grabs the flywheel for a split second, but as soon as the engine starts building compression the starter lets go. While I hear the starter spinning I also see the accessory belts spinning but very slowly. I thought perhaps the flywheel (automatic) got damaged. Took off transmission and couldn't see any physical damage. I am stumped. What could it possibly be? I am able to turn the engine over with a breaker bar on the crank bolt. It seems to turn over smoothly. Could it be that I got a defective starter? Please help.