all kawi 650 750 sxr rattle. it rattles because the drive shaft slips into the prop. its not a tight fit and it is going to and does make noise. as the splines on the shaft and prop wear, the rattle gets worse. since solas props are made out of butter stainless, they wear faster and rattle sooner. you can put it together with a bunch of silicone and it will be quiet for a minute or 2. i have never seen a kawi strip splines in a prop or on a shaft, but i saw a 550sx skat prop that was very worn.