put some wheel bearing grease on the axle going through the tensioner pully or purchase a tensioner pully with a bearing in it. Make sure the angle you put on the chain, when putting proper tension, isnt too much. Perhaps you should remove some chain links in order to have close to the proper tension before even having to use the pully, that way you will get the smallest angle on the chain going from rear wheel to engine. you should also ensure that the sprocket on the back wheel is aligned with the sprocket on the engine.