Ugh, I edited this. I was not totally awake, when I read your post. foe some reason, I thought it you were talking about your slide. the black tube is likey youe hose for the oil inujection, has a little brass connector on it .
I have trouble removing them too, I have just cleaned the carb around not taking the oil tube out. (its on the right side of the carb, aka clutch side.
of its on the other side, its likely the fuel line, and those, I just grip with pliers and carefully twisit it back in forth and that usually breaks the seal and will then start to slide off with a little help.
but that other line, with the brass hitting is the oil line, and theres a trick to getting them off and I dont know it yet. I just left mine on, when I was cleaning it.
Sporty