I was wondering the same thing and did a little looking around and from what i read everyone says do not try to clean them just replace them. Only way i heard to clean them without damaging them is with a torch or with electric parts cleaner. I heard brake/carb. cleaner is bad for them. I never tried either i just replaced them so i dont know if it works or not. I would just bite the bullet and pay the 40$ apiece. Just my opinion.
A wire brush carefully on the outside only (not penetrating the holes) is the only thing I've ever used on them.
I don't see why carb cleaner wouldn't work as long as you allowed them to dry completely, but then again, I probably wouldn't do that to one of mine unless I knew for sure.. so just forget I even said that.
I don't see why carb cleaner wouldn't work as long as you allowed them to dry completely, but then again, I probably wouldn't do that to one of mine unless I knew for sure.. so just forget I even said that.