Camlifter, if the chains don't come out even you use a tensioner on the pedal side not the motor side.
Since you are mostly riding with the engine going it would be more critical to not run a tensioner on the engine side so that you don't have to wory about the tensioner moving or breaking or causing the chain to not run as smoothly (there are also stories on here of the stock tensioner getting cought in the spokes, Ouch)
The tensioner used for the pedal side is excellent. It is light, small and mounts to a place on the frame that is already threaded and ready for it (where the derailer used to mount).
Another benefit is when you convert the pedal side to single speed you loose shifters, derailers, cables, extra gears/chainrings. You end up loosing 2-3 pounds and a lot of cluter. Also with that little tensioner on the pedal side it keeps the chain pretty tight and the chain never slaps the chain stays when you hit a bump. It is very smooth. Another thing is that the tensioner is spring loaded so you never have to adjust it.
Here is a link to one of these pedal side tensioners: Lickbike.com | Surly Singleator single speed chain tensioner