Ditto everytthing Tim said. Also - if you have the stocker out, try compressing it by hand (without changing the 'click' it was in when you removed it). You should be able to apply as much pressure as you can by hand without it collapsing. As for the sound, ditto what the other guys said. It's often heard only, or more prominently, on decel, and more when the bike's warm rather than cold (excess valve lash is the opposite - it usually improves with heat as components expand).