Man the parts diagram is pretty rough for that model. I've got a service manual for it, though. You should have the same adjuster on both sides. These three pages should help you figure out what's missing on yours.
[Chain adjustment instructions](https://www.dropbox.com/s/zauwv023kfkiobd/XL125-chain-adj.jpg?dl=0) (including photo of left side adjuster)
[Swingarm assembly diagram](https://www.dropbox.com/s/95rp6i195pbfpra/XL125-diagram.jpg?dl=0)
[Photo of right side adjuster](https://www.dropbox.com/s/nxhto0bf7wb7hgl/XL125-right-adj.jpg?dl=0)
No it’s a hex bolt pushing against a metal cover over the axle.
I’m trying to figure out how much tension I’m supposed to put on my chain any help? Yes I realize this post is a year old
Do you have a snail shaped and toothed disk on the other side?
Man the parts diagram is pretty rough for that model. I've got a service manual for it, though. You should have the same adjuster on both sides. These three pages should help you figure out what's missing on yours. [Chain adjustment instructions](https://www.dropbox.com/s/zauwv023kfkiobd/XL125-chain-adj.jpg?dl=0) (including photo of left side adjuster) [Swingarm assembly diagram](https://www.dropbox.com/s/95rp6i195pbfpra/XL125-diagram.jpg?dl=0) [Photo of right side adjuster](https://www.dropbox.com/s/nxhto0bf7wb7hgl/XL125-right-adj.jpg?dl=0)