Every once in a while, now that it has been warm enough to ride with the windows down, I hear a high pitch vibration that last about a second or two. I can usually hear it if I am just getting on the throtle up to around 20 mph. It sounds to be metal. It happens for such a short time that I can't pinpoint it. I have 60K. It doesn't sound like the ticking as in other post. Thanks for any help.