I reverse flush spray the filters out as well(except i use cheap degreaser) - the metal bodied walbro ones are especially prone to having the outside look fine, but the bits of metal under the filter medium tend to flake off - really powdery metal.
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The gauze filters don't take much to clog - even if there was some dust in the fuel line you used, it could do it after it gets flooded with fuel and flattens out over the filter. The fuel filters can also disintegrate on the inside and clog the filter with 'hair' - so definitely check it again

Last edited by Tyler; 14/11/18 08:23 PM.