It takes a bit of a keen ear but by moving the prop back and forth against compression you will be able to hear the reeds clicking. I personally doubt it's an issue with the reeds. My first twin was an old 3W 70. I bought it new but from a friend. Not knowing any better I set out trying to fire it up after getting it mounted in the airplane. On choke it would pop as normal but off the choke it would fire and quit very quickly. Just as I was giving up on it my buddy whom I bought the engine from called to let me know he had removed the reed block and had forgotten about it. So even without reeds you can get the engine to at least fire.