That part shown in your photo is a filter, if it had black bits in it, then its doing its job of keeping dirt out. Down side is it could now be blocked and preventing fuel getting tothe carb. Also means you have dirt in the fuel. Have a look in the tank to see if the fuel looks dirty. Take the filter off and reverse flush it by connecting it the opposite way round to the fuel pipe with other end (carb end) inot a clean glass jar. Look to see if any dirt comes out and the fuel flows freely, If you get lots of dirt and/or the fuel does not come out freely, then replace the filter. . My thoughts exactly , this fuel filter could very well be blocked or perhaps partially blocked. In fact , why have you got an aftermarket fuel filter at all? Most bikes I've owned have had filters built into the tank. If you feel the need for a fuel filter get a clear plastic one so you can see what's going on. Hope this helps,good luck.