Clanking noise

Hello guys:

I started to here a clanking noise at the motor area, not clear where it came from , it looks maybe from the upper part of the motor but sometimes I feel it came from lower. Not sure. I do notice that it goes out when I rev up the motor. It accelerate good, makes idle at about 900 to 1080 rpms. I runs good.

This link is a video that the sound can be heard.