That was the very first bike I motorized, Maniac!
The chain stays are round and I didn't account well enough for it and put the tensioner in to the spokes. It being a special rear wheel, and I didn't think/know it could just be relaced, ended up using a more conventual bike.
LOL, I made it from the end of the driveway to almost the end of the yard. Weird 2 minutes. "Will it start or not" Both made me a tad worried. Then She fired up and was ecstatic for almost 3 and a half seconds.
But was told there is a warehouse in NY State full of them. Parts and bikes.
Post lots of pics!