I’ve seen these guide/guards built around the rear cheater sprockets on a few old sleds. I know that back in the days these bikes were raced chain quality was pretty poor, and riders routinely carried extra links of chain and master links to repair breaks. So anything you could do to preserve and protect your chain, you did.
Tri-Angle Metal Fab to the rescue again. I bring them a cartoon drawing of a vintage guard, and one week later it’s on my workbench.
Pretty simple design
How the cheater sprocket sits inside of the guards.
As always, anything that Tri-Angle makes lines up perfectly.
Grade 9 spacers set the guard away from the cheater sprocket to give shoulder room for the chain.
Mounted rear view.
There you have it!