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  #1  
Old 03-13-2018, 04:37 PM
terry.mortimore terry.mortimore is offline
 
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Location: Sault Ste Marie, Ontario Canada
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Default 149 tooth ring gear part number.

Hi gang, I want to replace the ring gear on my flywheel assembly and Iím struggling to come up with a part number for it. My flywheel assembly has a 76628 number on it.

My engine is an original O-320 which I have been told are now called O-320 A.

Aero Instock list two numbers SL60882 and SL 72566. Can someone tell me which one would be 149 tooth?

Aero Instock are asking questions that I canít answer till the end of the week when I get out to the hanger.


Thanks in advance, Terry
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  #2  
Old 03-13-2018, 04:53 PM
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RV8JD RV8JD is offline
 
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Check out Page 4 of Section 1 of this link:

https://www.lycoming.com/sites/defau...g%20PC-103.pdf

Looks like you need the 72566 starter ring gear to go with your 76628 support assembly (but check me!).



Oh, Re: Hangar:



(Sorry, couldn't resist!)
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Last edited by RV8JD : 03-13-2018 at 05:05 PM.
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  #3  
Old 03-13-2018, 06:21 PM
terry.mortimore terry.mortimore is offline
 
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Location: Sault Ste Marie, Ontario Canada
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Default 149 tooth ring gear part number

Thanks Carl, thatís what Iím looking for.

Found a new one on E-Bay from the air boat guys in Florida listed for a good price.


Forgive my poor spelling, spellcheck let me down. 😀


Terry
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  #4  
Old 03-14-2018, 09:49 AM
mahlon_r mahlon_r is offline
 
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the support assy's for a fine tooth ring gear and a course tooth ring gear are different and not interchangeable. You engine sounds like it might have a course tooth ring gear support if it is an early 320. So you might double check that the fine tooth ring gear you purchased will work on the support assy you have.
Good Luck,
Mahlon
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  #5  
Old 03-14-2018, 10:33 AM
terry.mortimore terry.mortimore is offline
 
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Location: Sault Ste Marie, Ontario Canada
Posts: 199
Default 149 tooth ring gear part number

Thanks Mahlon, so itís possible that there is both a fine tooth and course tooth 149 tooth ring gear available?

Terry
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  #6  
Old 03-14-2018, 10:39 AM
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rv6ejguy rv6ejguy is offline
 
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Usually denoted as 122 and 149 tooth. Must use the correct one for the starter you have.
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  #7  
Old 03-14-2018, 11:39 AM
terry.mortimore terry.mortimore is offline
 
Join Date: Jul 2008
Location: Sault Ste Marie, Ontario Canada
Posts: 199
Default 149 tooth ring gear part number

Thanks Ross.

Iím trying to replace what I have. I know that I have 149 teeth on my ring gear, my starter is for a 149 tooth ring gear.

Carlís note last night pointed me at part number 72566. I found that one and ordered it last night. My confusion is if there is both a fine tooth and course tooth version of the 149 tooth ring gears?

I guess Iíll know for sure when my new ring gear arrives.

Terry
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  #8  
Old 03-18-2018, 07:07 AM
mahlon_r mahlon_r is offline
 
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sorry for the confusion, Terry. What I was trying to point out to you was that the flywheel or starter gear support for a 149 tooth ring gear and a 122 tooth ring gear are different. If you know you had a 149 tooth ring gear and are replacing it, it will fit on your current gear support..no worries. Older 320 had 122 tooth ring gear and that support and that support would not work with a 149 tooth ring gear. Someone, at some point, has updated your engine starter, ring gear and support from course tooth to fine tooth along the way.
Good Luck,
Mahlon
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  #9  
Old 03-18-2018, 03:14 PM
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RV6_flyer RV6_flyer is offline
 
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The 122-tooth ring gear is 0.375" front to back.

The 149-tooth ring gear (part number SL72566) is 0.440" front to back.

IF you were to put a 149-tooth ring gear on a support designed for the 122-tooth ring gear, the distance between the back of the starter ring gear and the front of the starter gear will be 0.065" closer to the starter. IF you use a SkyTec NL starter that was designed to be right at the Lycoming spec, you may have a case where the starter ring gear comes in contact with the starter gear when the engine is running.

I just measured a 122-tooth gear mounted on a support and a new Superior Airparts 149-tooth gear. The problem with the Skytec NL starter use to be documented on the Skytec website before the company was sold.

The above info may be what Mahron is pointing out.

From experience, I can say that changing a support designed for 122-tooth starter ring gear to a 149-tooth starter ring gear may work but it may not work. There may be a clearance issue with the 149-tooth gear. Supports designed for the 149-tooth gear have more surface contact with the 149-tooth gear than what is available on the 122-tooth gear. (aluminum to steel contact between the interface)
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  #10  
Old 03-18-2018, 03:25 PM
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RV6_flyer RV6_flyer is offline
 
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Default Photo

They say a picture is worth a thousand words.



The above image show a 149-tooth starter ring gear mounted on its support on the left. On the right is a 122-tooth starter ring gear mounted on its support.

Take notice that the AFT side of both gears are at the same location. Also note that the FRONT side of the gear on the left (149-tooth) goes forward more than the 122-tooth on the right.

IF you mount the 149-tooth gear on the support that is on the right, it will project AFT of the support housing and MAY come in contact with the starter gear.
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