maniac57 is correct, it is a motorbicycles.com heavy duty rear wheel kit, or like. It's what I have, I posted pics on rebuilding it.
The band brake will not safetly stop a gasbike alone! The explaination mark means I aint bee essen.
Couldn't understand what you meant by "...put some wire chip on it..." ?
I'm certainly no pro, but I'd guess the guy lined up the rear wheel, and the engine chain was tight, and the pedal chain was not, and he just put the tensioner over there because it was the easiest thing to do. I did research, and asked here, and now don't use any chain tensioner of any kind. Shorten your pedal chain to match the engine chain, and keep the axle as far back into the slots as you can- almost all the way is good.
Fantastic price. That is a deal, but I've still got you beat with the $50 DUI cruiser