Originally Posted by halflive
As far as i know a 90S should have holes in the airbox. Just as the later R100 has. I have two bikes with a replacement K&N filter. An R60/6 and an R100RT. There is no performance gain with the round replacement filter. Form, fit and function are the same as the original paper filter. The gain is in the reduced maintenance and the saving on new paper filters.
Just because there is SO much idiotnet 'data' out there that claims they don't filter as well as paper, I am going to repeat my opinion of the most important gain you get from using K+N's over stock paper filters: They filter a LOT better! I know of all the 'scientific' tests that prove the contrary but I know what I see. I see K+N's keeping air boxes and snorkel tubes a lot cleaner than paper filters. Some people have come back and have said that it is the dirt that you can't see and feel that K+N's don't filter well. Well, I am sticking with what I see and feel. Besides, you can look at the photos of those 'scientific' tests being done and see that the K+N's are being tested while perfectly clean with not near as much oil as they should have or barely any oil at all. Well, I can tell you that too: K+N's don't filter well lacking oil.