Need help: Video

Thats an odd one. That almost sounds like a "non meshing gear". It sounds out of sink with the engine idle. Where from the engine do you hear it? top end? Bottom end,Tranny?
 
It sounds like kick start is partially engaged,or engaging. Try moving the kick start around while it makes that noise. Have you had the engine appart recently?
 
When did this start happening? What was you or your buddy "Doing" at the moment this happened? Has the engine been worked on lately,or taken apart by anybody before this started happening?
After some answers,we can start to figure it out.
 
My dollar says balancer gear/bearing. My sound don't work so that's my guess.

Which ever went first on my motor it sure made a mess. X(
 
That sounds like it’s the countershaft balance gear, kick start idle gear, or the outer clutch basket. Pull the clutch cover off and inspect these items. Make sure you have a retaining clip on the kick idle gear. Look for contact marks. Make sure the rivets on the countershaft gear are tight. Check the flywheel as well as you may have dropped a magnet. Check that the primary drive gear is tight and check the nut that holds the clutch basket on. At any rate…….fix it before you ride it.