I add pre-filters to any filter system when possible and make them from vacuum cleaner bags cut to shape, held in place by tape or string or whatever.
Great minds think alike. Not that I use it very often but I have a Honda HRU19R 'Buffalo Buck' (GCV160) that has the terrible B&S style air filter box on the side that takes the rectangular pleated filter. While each filter comes with a thin foam pre-filter this still does a shitty job at keeping dust & particles off the main filter - and after every use it will have significant crap in the airfilter.
Sick of blowing this out with compressed air I took a synthetic cleaning cloth (it's almost like the stuff the surgical masks are made from) - cut to slightly larger size and placed over the filter (removing the foam prefilter as it's near useless).
The fit on those stock airfilters is a bit so-so as well - so I put a very thin layer of grease around the edges to give something of a gasket/sticky edge to trap any dust that does get drawn to it.
In comparison quality airfilters like on the GXV160 engine has near nothing in them - so definitely worth improving with some thin cloth or even a surgical mask material piece to assist keeping the main filter clean longer.
