Single-cylinder engine

• 1). Place the engine on a flat surface. Remove the key from the ignition.
  
  
• 2). Disconnect the spark wire from the spark plug located at the front of the engine. Plug the spark tester into the spark plug wire. Clip the other lead from the spark tester to the end of the spark plug.
  
  
• 3). Set the spark tester gap to 2.0 mm by twisting the adjustment screw on top of the spark tester. Start the engine and watch the window on the tester. You should see a strong blue spark. If the spark is erratic or non-existent; the coil is malfunctioning. If there is a strong blue spark move to the next step.
  
  
• 4). Shut off the engine and adjust the spark tester to 8.0 mm. Start the engine. If there is still a strong blue spark the coil is operating at optimal performance.
  
  

Twin cylinder engine

• 1). Place the engine on a flat surface. Remove the key from the ignition.
  
  
• 2). Disconnect the spark wire from the spark plug located at the left side of the engine. Plug the spark tester into the spark plug wire. Clip the other lead from the spark tester to the end of the spark plug. Make sure the other spark plug wire is plugged into the spark plug to ensure a proper reading.
  
  
• 3). Set the spark tester gap to 2.0 mm by twisting the adjustment screw on top of the spark tester. Start the engine and watch the window on the tester. You should see a strong blue spark. If the spark is erratic or non-existent the coil is malfunctioning. If there is a strong blue spark move to the next step.
  
  
• 4). Shut off the engine and adjust the spark tester to 8.0 mm. Start the engine and if there is still a strong blue spark the coil is operating at optimal performance. Remove the spark tester and plug back in the spark plug wire.
  
  
• 5). Repeat these steps for the coil on the right side of the engine.