How to Diagnose Ignition on a Harley Davidson 1200

Written by floyd drake iii
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How to Diagnose Ignition on a Harley Davidson 1200
Harley Davidson's classic V-Twin engine is manufactured in a variety of displacements. (Jupiterimages/Photos.com/Getty Images)

The Harley Davidson Sportster 1200 is one of Harley's most popular motorcycles. Smaller than the average "big hog," the Sportster first appeared in 1957 with a 900-cubic centimetre engine, which evolved into 1000- and 1100-cubic centimetre engines. In 1988, Harley introduced 1200-cubic centimetre engine. When motorcycles won't start, the problem usually lies in one of three systems: fuel, electrical, or ignition. Diagnosing ignitions on a Harley 1200 Sportster is the same as all ignition systems and is best accomplished through a process of elimination. Although there are different methods of diagnosing ignition problems, using an ohmmeter gives reliable ignition-testing results.

Skill level:
Easy

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Things you need

  • Phillips head screwdriver
  • Small flathead screwdriver
  • Ohmmeter or multimeter
  • Wrench set

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Instructions

  1. 1

    Disconnect the positive cable from the battery. The battery on Harley Davidson Sportster 1200 models is located under the seat. Remove the seat by unscrewing the Phillips head screw on the rear of the seat. Lift the seat off and disconnect the positive (red) cable from the battery with a wrench.

  2. 2

    Remove the electrical plug from the ignition switch. The ignition switch is where the key is inserted to start the Sportster. Raise the plastic clips on the side of the switch using a small, flathead screwdriver. The plug then pulls out of the switch assembly easily.

  3. 3

    Turn the ohmmeter on and set it to the "Rx1" setting. Touch the black and red probes together to make sure there is zero resistance. The meter reads zero when the two touch.

  4. 4

    Test the ignition switch by placing the red probe into the terminal connected to the red wire. The black probe goes to the terminal connected to the red wire with a black stripe. When both probes are connected, the ohmmeter reads zero, or very close to it. If there is any other resistance reading, the ignition switch is bad.

  5. 5

    Follow a spark plug wire to the ignition coil. On the coil, test the two smaller terminals by placing a probe on each terminal. When the ohmmeter is set to the "Rx1" setting, a working coil should read between somewhere below 3 ohms. Set the meter to "Rx100" and test the two larger terminals in the same manner. This reading should be between 6,000 and 12,500 ohms. If one or both of these readings do not match, the coil is not working properly.

Tips and warnings

  • The ignition switch and ignition coil are the primary parts of the ignition. If there are no problems with either, the problem is not due to the ignition system or is located within the engines distributor system, which is located inside the engine.

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