I might point out on the older series of Macs both piston port and reed valve that the air filter was the weak link .
It was only a single thin membrain that went between the air box and the cover .It had plenty of surface area but didn't stop stuff from being sucked into the carb ,chips, nuts ,bolts .More modern saws of course totally close off the path of junk bypassing the filters . You have to remember the time period on these things though .They were just about the same system of most saws of the time period .
Just about every Mac I've ever worked on with any hours on them shows some signs of dust ingestion on the intake side of the piston skirt .Doesn't seem to hurt them though .This by the way is not the only one I've managed to save that swallowed something .