Another little bit OT question which came up to my mind during reading the part about reasonance (and is haunting me for quite a time) is: I've read a lot about reasonant airboxes and stuff on how to perform a rough calculation of it. One particular note which almost every such article contains is: if you put foam inside the reasonator volume you will effectively cancel the reasonance. OEM GK75A/B airbox is equipped with foam-type filter. I expect that this filter effectively is cancelling the reasonance. I also know that 97-on B4s do have paper filters yet these are not exchangable with GK75s.The only paper filter I know that exists for B4 is K&N which costs about $100 per unit. And probably has to be replaced every season. The question here is how much the foam filter affects airbox ability to reasonate or vice versa how big improvement paper filter would be? If any at all. I have one piece of that K&N filter on hand but it is of unknown age and state so I am not planning to try install it into my bike.
Bandit Alley