Vintage Dirt Bike Q & A

I have a part that is basically an aluminum billet arm about 4-5 inches long with a rubber wheel mounted on the end. The guy I got it from had a bunch of billet parts from John Astleford (Jastco). I guess he made it.

I can not figure what this part is. Looks to be some sort of chain tensioner wheel or maybe a protector for the swingarm.

I have it mounted through the rear engine bolt and the wheel is just in front of the swing arm. But it does not seem to be doing much good. I probably have it in the wrong place..

I have a picture if anyone can help.

Thanks