Disconnecting spark plug cable with engine running can result in electric shock and death or serious injury. (00464b)
Do NOT pull on any electrical wires. Pulling on electrical wires may damage the internal conductor causing high resistance, which may result in minor or moderate injury. (00168a)
Fuel tank removal improves access to the center spark plug. Refer to the service manual or see a Harley-Davidson dealer for service.
Check the spark plugs at proper intervals. Refer to Maintenance Scheduling → Service Records.
  1. Disconnect spark plug cables from plugs by pulling up on the molded connector caps.
  2. Check spark plug type. Only use spark plugs specified for your model motorcycle.
  3. Check spark plug gap against specifications. Refer to Specifications → Specifications → Electrical.
  4. Always tighten to the proper torque. Spark plugs must be tightened to the torque specified for proper heat transfer. Refer to Specifications → Specifications → Electrical.
  5. Connect each molded connector cap until the cap snaps firmly into place over the spark plug.