I'm going from the stock 185 to 180 valve shims on the exhaust valves. My Yamaha Dealer was out of OEM shims. He found a couple of 180s that were loose, indicating that they came out of a motor and were saved. When comparing the stock 185s to the 180s I noticed the diameter was about 60% of the stock ones. Doesn't look like it could slip out of the cradle but just want to know how particular this needs to be.