help with bike tuning/repair

Sight unseen, I suspect that you rear derailleur cable needs to be adjusted ...

That is, the slack needs to be taken out of the cable when the chain is on the smallest cog ...

Check www.parktools.com.

From the look and sound of it, the barrel adjuster may need a turn or two.

In this image it's the cable adjustment barrel, also just known as the barrel adjuster, which adjusts the indexing between cogs. It also may need a turn as a new bike breaks in and the cables stretch, or settle. Turning this essentially moves the pulley cage in the corresponding direction. Even if there are no shifting problems, minor turns can help silence the drivetrain.

Here's a good vid that explains in detail. For your adjustment it may be the part starting around 1:50

Remember how many turns you made, and in what direction, and you can easily "undo" if you don't get it right.

Btw, that's for the chain noise - there are three random "clunks" through your vid which is hopefully just you knocking into stuff as you are filming. If those are the noises you are inquiring about and they are indeed coming from your bike, you got serious problems [IMG]/img/vbsmilies/smilies/biggrin.gif[/IMG]