Well, actually - I think it was a combination of the filter placement and the lack of protection from the rear tire.
It sure made the filter dirty on my 2013 (or '14 ?) Burgman 400.
I actually constructed and installed a baffle to give it more protection from the rear tire.
This is after maybe 4,000 miles.
conversely, my LIKE200i's airfilter stays clean for a long time - the end of the air-intake snorkel is so well placed within the panels!
Stig
(yeah - going through old pix - lousy weather here - going crazy low for the next 48!)