My 2007 1300S is completely stock. It has a new direct replacement K&N air filter. I recently installed remote AF adjustment so I needed to tune the carburetor. I was able to use the Honda tuning procedure in the service manual. The Bike's running great maybe even a little better than before I touched it. The spark plugs look really good. She pops, not real loud, when I get off the throttle or down shift. The popping doesn't bother me in the least. I'm just wondering if I should consider it normal. Should I be concerned with something like premature valve damage? When I say completely stock, it still has operation Pair valve system and complete airbox including snorkel.