So Ive started to notice my valves ticking around 3000 RPM. Stops anywhere above 3000 or below. I know the recommended service is to check them at 16000 Miles, my bike has over 21000 now and I highly doubt they were checked by the previous owner. I bought the bike with 18000 miles. Is it normal for these bikes to tick a bit? Ive heard that the engine casings are thin and I was wondering if others have this "tick"?