I have a 2005 hayabusa and I just changed my oil and spark plugs, the bike had 16,000 miles on it,and it was running rough,the oil smelled of gas. My mileage went from 45 mpg to 35 mpg so that was when I changed my plugs. The plugs were not bad at all, the electrodes were sharp not rounded, and the color of them was good. The bike after changing the plugs and before,would not idle smoothly, it idles from 1200to 1600 rpms. I put injector cleaner in the tank and it still idles the same.