I would bet that you have a sticky link (or links) in your chain. Put the bike in a stand, or lean it against a wall, then rotate the crank backwards by hand slowly. If you hear the "popping" noise, you will probably see a corresponding jump from the rear der. You'll also probably notice that one or more of the chain links are not going back to a straight line like they should when they come off the pulley. These tight links need to be freed up. Sometimes this can be accomplished just by working them back-and-forth aggressively by hand. Other times, the chain must worked on with a chain tool to get the links moving freely. Your LBS should be able to diagnose this pretty easily. It may be that a new chain is the easiest solution ... although if your chain and cassette have a lot of miles on them, you might need to replace both at the same time.

You won't notice this when you are pedaling because the pressure that you are putting on the chain pulls the sticky links free as the chain comes off the cassette. When you are freewheeling, you obviously don't notice it, because the chain is not moving.

razyfranco wrote:
Any ideas?

pedal forward.

agreed, stop doing that and it should take care of the problem

What, are you in the Circus?

WD40 is a solvent and can be used to free up sticky links.

Then wipe it off and apply some White Lightning.

That's chain lube, not the, ahem, bootleg cornlicker,

of course, maybe that would work too - as a solvent,

but basically it's a people lubricant, loosens up women anyway.

PoC