I recently installed a 520 conversion kit from motomummy which included driven sprockets and ek mvxz chain. My issue was with the chain changing slack and being almost too tight in some areas but then almsot too loose in others and it seems to be getting worse then better. I was told to contact Driven racing which I am awaiting word back from them. I narrowed the problem to be the rear sprocket. No matter how many times I spin the tire, forward and reverse, when ever the driven symbol on the sprocket is between 11 and 3 oclock the chain is loose and whenever it's between 4 and 7 its tight again. I placed and object as close to the rear tire as I could and spun it around to see if the bearing might be off but it seems to stay the same all the way around. Tires only have 500 miles on the. The bike is an 03 with just over 7k on it. If anyone has any other insight it would be greatly appreciated. I've spun the tire checking it at the same locations in a row and even spun it around numerous times and came up with the same conclusion. Hopefully they wont make me tear it off and send it in while my bike sits on stands this early in the season.