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Lycoming starter ring gear

larryMar

Well Known Member
To save me the math, and trip to measure the starter ring, does anyone know:

how many degrees is each tooth, or the diameter of the ring?

I believe that they are all the same, but specifically on an o-320

Thanks
 
Going from memory, there are two different starter ring gears. 122-tooth and 149-tooth. Both have the same diameter.

The 122-tooth is thinner (front to back) than the 149-tooth gear. I have put a 149-tooth gear on a 122-tooth support. It will work with most starters but the SkyTec NL starter could have issues.

How many degrees per tooth? I would calculate that as 2.95=360 / 122 or 2.416=360 / 149.

I have a new unused 149-tooth ring gear in the hangar that I can go measure BUT I do not have a caliper that larger so will not be able to come up with an accurate measurement.
 
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Thanks,

I have 149 teeth, but I don't know the diameter. I didn't know that they made the 122 one...

Thanks again
 
Somebody can check my math, but a 149-tooth gear has a diametral pitch of 12 (per some Lycoming docs I found), which means a diameter of 12.416", or a circumference of 39".
 
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