Today I finished up some of the wiring on my 83 and decided to give a couple of the systems a test run. I wanted to make sure the starter would turn over and that the ignition switch was working properly, so I gave it a couple of quick turns. The starter spun and it sounded like the solenoid threw out the gear but it made a terrible grinding noise. The starter is from my old 12A and I've now got a 13B. Is there a difference in the starters? I know that the engine came with a lightweight steel flywheel but I'm unsure of the brand or part number. I'm going to pull the starter tomorrow and see if I can possibly see what the issue is. Until then any help/thoughts are greatly appreciated.

 

I think your starter is bad. Judging by the rust on everything else. Take it out and test spin it on the ground. Observe how quickly the gear jumps out and how fast it spins. Then see how fast it jumps back when power is removed. Or take it to a local auto parts store where they test starters.

All starters from 74 to 92 (NA) 12A or 13B are compatible. I've currently got an S4 NA starter in my REPU because I needed one that worked right then.

 

I figured they were the same but just wanted to be sure. The starter should be good. It was working great when I was trying to get the 12a going. I'll pull it in a bit and check it anyways. It's a weird sound it's making to. It doesn't sound like the teeth are grinding but more like it's hitting the side of the flywheel. Maybe it has a bad bearing inside making the noise. I guess I'll find out soon enough hopefully. Thanks Jeff.

 

there is 9 ( earlier than s3 rx7 ) and 11 ( s3 and s4 NA ) tooth starters

and despite what you read sometimes,, they actually do interchange on the same 300 mm ring gear

i also have mixed and matched them with zero issues

methinks its done a little like the speedo bur drives,, when the tooth count and bur diameter changes,, so does the offset from the centerline so that both can interchange despite appearances

 

I got it figured out. The gear was jammed. Jeff was right about the rust. The gear wasn't moving out far enough to engage the flywheel. I cleaned it up and greased it and now it works great. Thanks for the help.