I know this is not a bike tech thing per se, but I do have a few bikes and it seems related. Plus the Miata has some of the spirit of bikes 'cause it's small and light and top down, and the machine does handle.
I have an '04 Mazda Miata and I do my own wrenching. I replaced the air filter a while ago with an OEM Mazda air filter from West Coast Mazda in Port Moody (Made In Israel 0201-2 2).
Yesterday when I was changing the oil I noticed that the top half of the air box buzzed against the bottom half of the air-box when I revved up the engine to warm the oil.
The air-box is split horizontally, the top half has the vacuum intake side and the bottom half has the intake snorkel side.
I wiggled the top half of the air-box (which has the vacuum intake side) and noticed that the top half of the air box did not seal tightly against the bottom half. It had perhaps a 1/8” gap.
I am worried that since the top of the air box is the vacuum intake side and it was not sealing fully, unfiltered air would be sucked up and shorten the engine’s life span.
I had a Fram CA8601 air filter and I compared it to the OEM Mazda air filter and the OEM filter clearly had a noticeably thinner perimeter gasket.
I replaced the OEM filter with the Fram CA860 and buttoned up the air-box. It was easily noticeable that the top of the air-box now compressed against the thicker gasket of the Fram air filter and the top of the air box was firm and did not move around.
The only positive thing about this negative experience (pun) is since the top of the air-box is the vacuum intake side, the pressure difference may have helped hold the OEM filter up and in place.
The OEM filter was moderately dirty and I did not see any dirt in the air-box top, but that is no assurance against increased engine wear.
I believe I should go to the dealer with my OEM Mazda air filter and be compensated for the potential damage of my engine sucking in unfiltered air, but I am not sure how to go about this.