What you did is the essence of "hot rodding" and it can be fun. It also can be a nightmare! Most of these starters are with PM (permanent magnet) fields so you cannot wire them up incorrectly since there is no wire. You can, however, get the magnets 180 deg out which will reverse the direction of the motor. Next, the shaft may not be the right length and the starter pinion may not engage. Ya gotta study and measure this stuff CAREFULLY to get it to work.