A motorcycle mechanic's main duties are to service, inspect, repair and sometimes build motorcycle engines. Some duties that a motorcycle mechanic regularly performs include running diagnostic tests to determine what is wrong with the motorcycle, checking ignition points on a motorcycle engine, replacing spark plugs, inspecting and replacing brakes, overhauling engines or electrical systems on a motorcycle or making major repairs due to an owners accident or neglect. Often times, motorcycle mechanics will test drive a motorcycle that comes in for repair. This is done to help diagnose motorcycles issues and to decide if the motorcycle has been repaired correctly after all repairs have been made.