Two strokes seem to suffer from poorly filtered air much more than four strokes.
Why? Because they draw intake air on every revolution vs everyother for 4 strokes, plus all this air must pass through an oil covered crankcase where the grit will be trapped & injested later vs the 4 stroke washing it away in its oil bath.

Well filtered air is very important, no matter 2 or 4 stroke. Using fenders will keep the air around the intake filter cleaner as well as the rider.