I am a Truck Mechanic and yes think in that same way when Building most everything . Well on just about all cars and Trucks today they run Belt Tensioner's and sure it keeps an even Load on the Belt making it track much better and preventing it from walking off . I ordered a 80cc Super Rat kit and once it's Dialed in I want to run it all out . I was thinking that Chain Tensioner would be a real good add on . I found this one after searching the Forum Better yes I am new here . Also I am seeing that I might be better off Looking for a good older bike with stronger rims and spokes .
Here is that tensioner but Looks kind of Light duty ? Spring Loaded Chain Tensioner for Gas Motorized Bicycle Plans | All Parts | Parts for Gas Powered Bicycle Motor Kits | Live Fast Motors - Gas Motorized Bicycles and Gas Powered Bicycle Motors