It could likely be the tensioner needs the right adjustment. The roller bolt and bushing assembly for the tensioner could be pre assembled backwards causing the chain to wobble. Set the center of the bike on a stand and lock the clutch lever with a zip tie or if you have a lock button on the lever, now turn the peddles and watch the chain as it travels around to make sure that it's running evenly and not binding any place and is well centered on the rear sprocket. Also, be sure to have a straight chain line when you look down the back of the bike and check to see if the rear sprocket has moved some after some rides also, if that happens then you might have to add some washers or shims, locktight or set screws ect. to keep the rear sprocket assembly in place.