First I would check that all the wires are hooked up correctly. Next check the battery cables and the ignition fuse. Next I would check the solenoid. Good luck
If it is installed incorrectly and causes the starter to be engaged continuously/always running it would kill the starter fairly quickly.
improper engagement of bendix gear to ring gear was my problem
first make sure that you have a fully charged battery. if you do and turn the ignition on and do not get even a clicking sound see if the starter is good it could also be the ignition switch.so check that and all your fuses. also make sure that all your ingnition wires are seeted properly.
the starter
starter motor need overhaul
Assumeing it's the same starter, the bendix(the gear on the end of the starter that engages the flywheel)could be bad, and or the starter it self could be bad. sounds like number of teeth on new flywheel does not match number of teeth on starter. find out from mechanic that installed new fly wheel, how many teeth on flywheel if he doesnt know, a ford dealer can tell you from the part number on your receit. then ask how many teeth should be on starter to match fly wheel pull starter and count teeth
Loose connection? Bad starter (flat spot)? Bad starter solenoid?
dead battery
Starter misaligned? Starter engaged with engine running? Metal fatigue?
you can find information on a starter of early miatas on: http://www.racecaddy.com/mx5/tech/starter-mx5.html They have location, causes of failure and how to change it
It can be a defective starter assembly that causes this problem. There are two parts to a starter assembly: the starter motor and the starter solenoid. The offending culprit is usually the starter solenoid, and it should be replaced.
decribe two causes of higher than normal starter current draw