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Lycoming Flywheel Starter Ring Gear Teeth

Vans101

Well Known Member
I think my starter ring gear teeth need braces or something...

My STech starter has been making some strange noises so I investigated the flywheel and attached is a picture of what the teeth look like.

It looks like the starter has run along the side of the ring gear instead of meshed with the gear correctly.

The starter teeth look great.

The engine is a Lycoming and it has about 15 hours since overhaul from a reputable shop and I did not notice that the teeth looked damaged when I put the engine back on and I had to install the flywheel during the process.

The airplane also had an annual condition inspection since the overhaul and I remember the A&P specifically looking at the teeth and he did not notice anything.

So now I am wondering if this ring gear is still serviceable.

If not does the ring gear get removed and replaced on the existing flywheel?

If I need a new flywheel will that affect my engine balance? I know the connecting rods were static balanced but I do not know about the crankshaft and flywheel assembly.

What could have caused this? There does not seem too much that I could have done wrong and the overhaul shop was the one that installed the starter and they ran the engine on the stand a number of times.

Any help/ advice would be greatly appreciated.

THANKS!!!
 

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  • Flywheel.jpg
    Flywheel.jpg
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It's supposed to look like that. Those "features" are there to help guide the starter teeth into the ring gear when the solenoid pushes the gear forward.
 
If the starter gear and it's shaft are not lubricated well enough, the gear on the starter bendix will not slide forward and backward easily enough to engage/ dis-engage properly and it will make a grinding noise. Tri-flo or a similar teflon/silicone lubricant will work well.
 
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Ring gear looks like it will work fine to me. They make a shim for between the starter and the crankcase to get proper backlash of the teeth. You might try installing that. It helps with the weird starting noises.
Merry Christmas,
Mahlon
 
Looks like the corners of the teeth have been ground on. I would try the shim on the starter. I have one if you have trouble rustling one up.
 
Thanks everyone for your help!!!

>Looks like the corners of the teeth have been ground on. I would try the shim on the starter.

When I first looked at the flywheel I could see the cut outs for the starter teeth to mesh in with the flywheel teeth (shown with the green arrow in the attached PDF).

Then after carefully looking at it I can see that there are additional small divots in the flywheel teeth (shown with the red arrow).

What is this shim called? I assume that it is just a thin spacer that drops the starter down just a bit to move the starter teeth outward from the flywheel?
 

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  • Flywheel Teeth.pdf
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To answer another part of your original post, yes you can replace just the gear tooth part of the flywheel (ring gear). I had to replace mine after a couple starter kick backs damaged it. I took my flywheel to Signature Engines, and they replaced it, although you can do it yourself. You should research this online if attempting it yourself. I think I read that you whack the original gear with a chisel/hammer to break it. It comes off easily. Then you put your flywheel in the freezer and heat up your new ring gear. Quickly assemble the cold flywheel and hot ring gear. Should slip on easily, but cooling of the ring happens quickly, so don’t linger. Cooling/warm up happens and the ring gear is there to stay.
 
The little smaller divots on the teeth look like the starter got re-engaged after the engine was running for just a moment, or not fully retracting quickly enough and perhaps some slack or lag in it's retraction. The reason abuse marks are not showing on the starter drive gear is that it is considerably harder than the ring gear teeth.
 
If you haven’t lubricated that starter gear, maybe you should. To do this, use a wide blade screw driver, or some other flat tool, and pry the starter gear forward from behind, exposing the shaft it rides on. It’s spring loaded, so you’ll need to hold it forward while you spray some lubricant on the shaft. This allows the starter gear to freely move during, and after start as it’s supposed to.
 
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