Authorities are citing speed as a factor in a fatal motorcycle wreck that killed a South Carolina man Saturday on Cothran Road. Mark Harmon, 50, of Aiken, S.C., died at the scene after losing control of his 2006 Victory motorcycle in a curve, authorities said. Robin Stone, spokeswoman with the Georgia State Patrol, said Harmon was attempting to negotiate a curve “at a rate of speed that was too fast for conditions” when he was ejected from the motorcycle and thrown into the path of an oncoming vehicle.