i was wondering if you bought a starter that came of an 85 12a engine will it be a direct bolt on to an 81 12a? or will there be a difference , im hearing that there are different tooth sizes but im not quite sure

 

AFAIK, all rotarys (12a vs. 13b) and all years use the same starter, except for the automatic transmission units, which have a different number of pinion teeth (11 vs. 13, IIRC).

 

ya i believe they were they same on all years

 

Aaaah, not exactly. All "FB" starters have the top bolt hole threaded and the bolt comes from the front and threads into the starter. The "FC" starters are not threaded and use a longer bolt and nut. They are interchangeable, just remember if you grab a "FC" starter you need the nut and bolt that comes with it and visa versa.

 

There are different size gears on the starter. I don't know the exact years each was used, but I know a 79 starter would not work after I dropped an 85 12A into the 79. I had to grab the starter off a dead FC, as the 85 was an auto.
This really had me baffled, because I compared the flywheel and ring gear diameter of both the 79 flywheel, and the 85 flywheel I swapped onto the formerly auto engine, and they were the same. The ring gear needed replaced on the 85 FW, so I placed it against the 79 FW, and the ring gears were identical. Yet, the 79 starter would not engage the 85 FW.

 

There might be a variation between "sa" and "FB" 7's.

 

Check these listings. I would say that auto's are divverent and early SA's are different. http://www.autopartswarehouse.com/se...h=Mazda%20RX-7

 

At these prices you can see why i keep a couple spares. I got a FC one for free, and I scored what looked like a fresh rebuilt at the pick-n-pull for $25

 

i've used the threaded / non threaded ones interchangeably. mostly thanks to a drill

 

The auto is way different. As for SA/FB, I dunno exactly when the change was made, but I know it was made. I would have thought that since the flywheel ring gear was the same, the original 79 starter should have worked, since the trans was also the original 79. But, I was wrong. It needed the later style larger starter drive to engage.