I have a tight spot on my chain, tight 15mm play, the slack part I can almost push 2 inches of link onto the under side of the swing arm (794s Black swing arm), I have a gold X ring renthal chain which is new (only about 500 miles) I have put a mark on the chain at the tight point, I then do one rotation and the same mark is now the slack part. I then do another rotation and it becomes the tight point again. The wheel is in straight, the sprockets are also brand new. what is wrong here? help please