Hey guys I’m new here and new to the cbr world, I am looking at a 2005 cbr1000rr and when it is started there is a knocking , previous owner said it never did it before and he was riding and it started to knock and he shut it off and hasn’t started it since except for a video for evidence for sales, I am very interested in this bike it has low mileage I just want to know if I should be worried , what I should look for , or what the possibilities could be , could it be a top or bottom end issue ? Could it be valves ? Or could it be as simple as a rod bearing ? Any help would be greatly appreciated... thank you!!!