The Snug-A-Bug is a small device that keeps the engine from vibrating backwards and loosening your chain.
It also turns chain tightening into a one person job.
The Snug-A-Bug is a product of my own design, and is fabricated in my shop in NE Ohio. I made this back in the 90's and have sold...
http://www.diygokarts.com/vb/attachment.php?attachmentid=78819&stc=1&d=1479215405
This is what I came up with in the mid 1990's, My first prototype was exactly like your first photos, it brought back alot of memories.
With this set-up you can weld it on or drill and bolt it on, I too went...