I usually spray that with WD40 first,leave it sit for 15 minutes or so then spray it with Gumout carb cleaner,followed by air.
And flammable as all heck. Don't even think about fire while you use it. A great industrial solvent, we used it to clean sheet steel and pipe in the welding shop I worked in as a teen. Cuts grease and varnishes better than most anything.Varsol....a lot cheaper than that other stuff...and it works.
I do the same exact thing when cleaning out old carbs. I could not clean the original carb off of my 318 to save my life. I tried wires, tip cleaners, had a local shop soak it for days. The tractor kept on surging, no matter how many times I cleaned it, and blew air through it. Also, the carb on a 318 has a little freeze plug looking cap that will blow out if you use to much air pressure on it.I do much the same too--I pluck a bristle out of a wire brush ,and use copper wire too,which is unlikely to hog out the holes in the jets..sometimes I use torch tip cleaners if I have them handy too,but those can enlarge holes easy if your careless or use one too big!..stiffer wire is a lot easier to use than soft stuff like a bread tie..(but pokes your fingers easier too!)..
I find blowing carbs out with air is OK,the higher the pressure the beter--but on Tecumseh carbs I've blown that seat for the needlve valve into iblivion a few times,its best to apply air from the needle valve side only on those!...
Yes, the white death, once the manufactures coating has been breached, it really doesn’t matter what you do, it will simply progress. If in fact that is what it is. Good luck.:trink40:White varnish cyrstals everywhere! Have you ever had this problem