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From what I'm seeing on both bikes, the failure is indeed vibration related.
I don't really like the forward mount having two parallel arms instead of triangulation or a transverse mount. If the two bolts at the rear of the skid plate don't securely clamp that portion, the front is allowed to vibrate even more.
Cyclic vibration fatigues the metal and breaks the grain boundaries at the edge that is most under stress (tiny crack). Once the crack is started, progression accelerates which allows the plate to swing further in vibration, in turn bending the metal more and more.
The dusty/powdery looking rust is the result of the edges rubbing back and forth against each other. This is something to keep in mind every time you work on any machine, a streak of reddish brown is a sign of iron oxidation and the cause should be investigated as soon as possible. It may be something as simple as a motor mount plate needing the bolts tightened. With aluminum the clue is white powdery residue.
Just my 2 cents worth, so feel free to ignore it.
Jay Littleton,
Former Nondestructive Inspection Technician, USAF (ret'd)
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