Perplexes my mechanic

[jononation]

Just got my bike. Upon first start, there was a loud knocking sound coming from the top-end of the motor. So I shut it off after a minute as I realized that this is not a normal sound!

Brought it to a bike mechanic to fix the loud knocking in the motor. He turned it on and right away shut it off as soon as he heard the sound. He then took apart the whole top-end and most of the rest of the motor, looking for the cause of the sound.

Everything was in perfect condition! He spent a total of 6 hours searching for the cause of the sound and couldn't find it. He's been a motorcycle mechanic for 25 years, so he has experience. This has totally perplexed him!

So after all that, we determined that we couldn't fix it and since everything has checked out fine, maybe this sound is more normal than we thought.

The sound seems to disappear at higher speeds.

Anyone know anything about this kind of sound coming from the motor?