Muffled clacking sound.

[Uzi9mm]

Went ridin today.  Sometimes when lugging in 2nd or 3rd and lettin off the gas I heard a new sound almost like a muffled clacking.     I usually run 100LL and H1R at 40:1 but the last 2 tanks have been (7 eleven) 92 octane.  Could it be knocking?  Or, something more serious?        

[hughes]

If the chain is worn out it will make a clacking sound. What's the condition of your chain?

[Uzi9mm]

Yes, my chain is worn out.  I keep it adjusted and well lubricated but I need a new front sprocket and a chain.  I will replace them.

[hughes]

How worn is the rear sprocket? I always try to replace sprockets and chains as a set. I think this will give better service life from all three componets.

[Johnniespeed]

Every time my KX500 has any type of unusual noise, it has been related to the pipe mounting. First the upper mount broke off, another time the lower rubber mounts broke. Another time the springs fell off. Another time the pipe cracked.
  I cannot hear your noise, but if it was my bike, I would look at every pipe mount first.
  Due to recession, this is only my one cents worth.
  John

[Uzi9mm]

Rear sprocket is in great shape.  The teeth on the front sprocket are starting to lean in one direction.  I will check the pipe mounts.  Thanks for the replies.

[Hillclimb#42]

Good advice. Better joke on recession.

[Uzi9mm]

The upper pipe mount is broken.  I have a new one but I wont be able to test it for another week and a half.  Thanks for the advice.