I have a 2007 Kawasaki ninja 500r that makes a clunking noise at low speeds, the noise seems to stop somewhere between 30 and 40 mph. If I accelerate slowly it doesn't seem to happen but does pretty much every time I accelerate quick but not like full throttle acceleration. There's no sound at idle. Any ideas? I'm scared that it's a piston issue which will probably cost an arm and a leg as I don't really have experience tearing down the motor. It has 23k on it and just had an oil change a week ago as someone asked if I had checked the oil level. Other than the noise it runs great. I purchased the bike 2 years ago used and I've put about 3,000 miles on it. The noise started last year at the tail end of summer and now that the weather is getting better I'm wanting to ride. I rode 16 miles on it today and the clunking noise is still there. Any ideas are appreciated. I pray it's something simple and not something expensive like a piston issue.