Tensioner
Hey suitcase, Almost any bike can be set up to run without a tensioner. It's a simple matter of getting everything PERFECT. You have to get the engine in perfect alighnment with the rear sprocket. you have to get the rear sprocket set up with NO in-out or up-down wobble. Then try to figure out the motor chain VS. peddle chain lenght. On a single speed bike they hardly ever work out the same. Then there is always the issue of frame clearence. On some bikes the only way to clear the frame with the chain is with a tensioner.
The tensioner solves a lot of problems for me. And if set up right works very well. Motorpsycho has his bikes set up without them,But he's a perfectionist. (Thats a compliment Moto.) Honda and Yamaha don't use them either but they have computers to figure it out for them. I just don't have that kind of patience. And like I said, If set up properly they work just fine.
With all that said, If you can get your bike set up to run without one it would be one less thing to go wrong. Tensioners, once in a while, Will SNAFU and that involves ripping out spokes and warping wheels. It's a lot of work, but if you can set it up without a tensioner, go for it. It will be fewer problems and make for a cleaner build.
Big Red.