Is this thing supposed to be loose?

[JohnC]

I have a Yanmar 3 cylinder Diesel in a John Deere X758.
This little silver/aluminum cover fits on here loosely and vibrates back and forth when the engine runs. Is that correct? Here's a video:

https://photos.app.goo.gl/6oiGaCTVUBm3Ugxd9

[DmaxMaverick]

I wouldn't think so, or maybe it doesn't matter. What is it covering, and is it loose with the engine off? What holds it in place? It looks like it's just a cover. Maybe try some duct tape. If it has no affect on running, crimp it or use some safety wire as a permanent solution. That would drive me nuts, unless it's supposed to move like that.

[JohnC]

What is it covering,

Don't really know. I was hoping someone else would.

and is it loose with the engine off?

Yes, it rotates freely and moves up and down slightly.

What holds it in place?

I think it snaps on. If you look closely near the bottom you can see a tab that is bent inward. I think that is what keeps it from popping off.

[JohnC]

I just took a closer look at it. If I had to guess, I'd say it is an anti-tamper device for the throttle stop. The black bit sticking out appears to be threaded and have a screw driver slot in the end. There are three tabs near the bottom that prevent it from being removed. It is free to rotate completely around.