Lycoming O-360 ring gear

Hey all. Now that my holiday travels are over, I'm planning to do some
maintenance to my Cherokee. The ring gear has gotten chewed up over time, and now
will sometimes not disengage while the starter is rolling it over. Worn/broken teeth,
etc. I was pretty sure it was a 122-tooth model, but when I looked at it yesterday,
it had the rounded tooth bottoms like the 149. I've got a Skytec starter on it (I'll
have to look up the model number to be sure which one).

Anyway, I think it's quite possible that the wrong ring gear is on the engine.
What's the deal with the two models? I've heard conflicting reports that the older
Lycoming had 122 and then changed to 149. I've also heard that only the O-235 and
O-360's have 149s. I suspect it's probably the former and a mish-mash of
disinformation and ill-fitting ring gears. Since I need to replace the old one, I'm
confronted with the choice of which to get (at least until I verify which starter I've
got)

Questions:
- What's *supposed* to be on an O-360-A3A in a PA-28?
- Is one better than the other?
- How many people have the wrong starter/ring gear combo? I suspect it mostly works,
but probably wears quickly... probably what I've got going on.

Cheers,
-Cory

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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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