A speeding motorcyclist is dead in Hurst where police and paramedics found a disturbing scene early this morning.  About 1 a.m. a man rode his Harley into the back of a big rig on Highway 183 near Hurstview, leaving a path of debris for at least 100 yards.  There was nothing the paramedics could do because the rider was obviously dead on impact.   Because of the extensive crash scene and the lengthy investigation, traffic was backed up for hours overnight.