Dang you have a good eye!
You should go to work as an AC inspecter!
If the striped off and went through the gears, chain etc that would explain the carnage

 

Does the chain tensioner move up and down, up and down or does it slowly inch up one tooth at a time as the bike ages and the chain stretches?

Thought?

 

Here is an image I found in another thread here on the forums...

 

Part is an investment steel casting I think. The teeth could have been a broaching operation. Part is case harden. The second generation of this part, the smaller other part is relieved of teeth since the older full tooth one hung up. When first installed, it is held down with plastic tiewraps. When all is installed, the first fwd movement lets it push up and take up pretty much all slack. Then as chain and sprocket wear occurs, it will move only when slack freeplay allows it to jump one buttress notch. Until then, it is locked.

If that is one one the teeth, it may have broken off at the initial adjustment. One advantage is the auto tensioner has two heavy coil springs that tension primary chain but do allow some up and down.

The manual one is totally locked and adjustment are greater lengths. They can be a tad noisier. The auto one when the primary chain wears uneven as most chains do will overtighten near the end of it's life. Probly at over 100K or people who drag race their bikes between red light as some do.

 

Since you are in there you might want to look into replacing the adjuster with the Baker attitude adjuster. If you search the forum you can see the issues with the stock adjuster. It can over tighten and screw things up.

Phil

 

Time to replace with a Hayden unit. Good eye Larry!

 

See this piece right here, that looks like threads from the case. You sure the plug wasn't cross threaded and those shavings aren't the threads that came out.

 

That was the teflon tap....