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Lycoming Starter teeth to flywheel teeth...what do I need?

W

William

Well Known Member
How many tooth flywheel do I need for my Lycoming O-320-B2A?

I have a Lycoming O-320-B2A with the stock starter and I'm in need of the flywheel/pulley assembly. I'm not in my hanger to count the number of teeth on the starter, but I need to know how many teeth are on the starter to go with a 149 tooth flywheel, and 122 tooth flywheel respectively. SO when I get to the hanger I can count the teeth on my starter so I know which flywheel assembly to buy. Thanks in advance for your help.

Bill
 
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William said:
I have a Lycoming O-320-B2A with the stock starter and I'm in need of the flywheel/pulley assembly. I'm not in my hanger to count the number of teeth on the starter, but I need to know how many teeth are on the starter to go with a 149 tooth flywheel, and 122 tooth flywheel respectively. SO when I get to the hanger I can count the teeth on my starter so I know which flywheel assembly to buy. Thanks in advance for your help.

Bill
Click to expand...

Bill,

The starter should have the "pitch" indicated on the data plate. A 10/12 pitch fits the 122 tooth flywheel, a 12/14 pitch fits the 149 tooth wheel.

John Ciolino
RV-8
N894Y
 
Hi John thanks for the information, that is exactly what I needed to know. :)

Bill


John Ciolino said:
Bill,

The starter should have the "pitch" indicated on the data plate. A 10/12 pitch fits the 122 tooth flywheel, a 12/14 pitch fits the 149 tooth wheel.

John Ciolino
RV-8
N894Y
Click to expand...
 
Tooth pattern

The 149 tooth (12/14) ring gear has a "U" shape to it and the 122 tooth (10/12) is more of a "V" shape. That's a simple way to figure it out.
 
I checked the starter today and no pitch was indicated on the data plate. The starter has 9 teeth and they have a v appearance to me. I did get the following numbers off of the starter; does this help? I checked my lycoming parts manual and that was no help :(

Delco Remy 12V

model 1109657
serial 7385


thanks
Bill
 
Ok I've narrowed it down a little. I know now I need a 122 tooth 10/12 pitch ring gear, but what pulley do I need? I have a Denso 12v alternator with the following part#18504-6220. The outside diameter of the pulley is 2 14/32" and the inside diameter of the pulley is 1 14/32" with a groove approximately 3/8". What diameter pulley do i need on the flywheel, the 1.91:1 or the 3.25:1?

thanks,
William
 
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Pulley size

William,
The lower ratio drive (1.91:1) has the smaller pulley used with a generator and the higher ratio drive (3.25:1) is used with an alternator. It gets wonky because the older narrow deck engines had the V (122tooth) ring gear and had generators so they had the smaller pulley diameter and then newer wide deck engines had 149 teeth and alternators. (I'm sure there is some overlap so don't jump on me whoever you are that knows of an exception).
If you're going to stay with your current starter then find a 76628 ring gear support (ECI makes them as AEL76628) (large pulley) and have a Superior SL60882 122 tooth ring gear put on it. Lycoming Service Instruction 1141 tells you how.
Hope this helps. Grub
 
You might be better off with the smaller pulley on the flywheel if you are running an automotive alternator. Due to the fact that they have a much smaller pulley than aircraft alternators and you will be over speeding the alternator.

Look at the pulley that drives the alternator on your car. Your car motor lives under 2000 rpm most of it's life.
 
Sorry to revive an old thread, i have that same issue small pulley 1.91:1 does anyone know if there is an issue running this ratio with the vans supplied automotive alternator?
 
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