Just put a K&N oil filter on my SB when I changed the oil this weekend. It made a world of difference in the sound of the engine especially the sewing machine in the top end, I assume it is the better flow of oil to the top end. The old filter may have been clogged up but I don't remember it getting this quiet when using a Harley filter at the last oil change.

Has anyone else noticed this after switching to K&N or any other filter other than Harley?

 

Did you use the same oil that was previously in the SB?

I just changed mine using an KN-171C as well as changed all fluids to Mobil1 brands. V-Twin 20W50 in Engine
Racing 4T 10W40 in the primary
75W90 Gear oil in the Tranny

I didn't notice any difference in sound but I do have V&H slipons which are louder than stock..

 

No, it was the same weight but different brand.

I used Castrol -Power RS V-Twin 4T 20W-50 full synthetic, last time was Mobile 1 syn.