<HTML>Problem: Bobbling hammers on a S&S M from C5 on down. I mean, they don't even check on a hard blow.  Some of them are checking, but only on a hard blow. The rest just bobble. New hammers, shanks and flanges. Let off is right, drop is right, there is after touch. I changed let off, I changed drop.  Keys are level, right amount of dip.  I increased dip, decreased dip. I've increased rep spring, and decreased rep spring. Dampers are not in the way. Nothing. This is a 1939 model. There has been some discussion about knuckle size.  As I said, these are relatively, (about 3 years old) new h/s/f/ , with 3/8" knuckles. Could that have an effect? Wim </HTML>