Many electrical problems are the result of engine vibration, heat and moisture.
Throughout the years, Harley-Davidson motorcycles have become notorious for having wiring and electrical problems. Engine vibration, exposure to the elements, and sometimes poor manufacturing techniques have created roadside delays for many motorcycle enthusiasts. Accordingly, the manufacturer has gone to great lengths in recent years to produce a higher-quality wiring harness for its bikes. Excellent connectors and high-strength wiring and welds have begun to reduce the frequency of repairs. Nevertheless, problems can and do occur, requiring a knowledge of troubleshooting and repair.
Most wiring–whether it’s automotive, hobby or household–can generally be repaired with a quality soldering iron and a bit of know-how. When a broken electrical wire on a motorcycle is discovered, begin by stripping both ends with a pair of wire strippers. Cut an appropriately sized piece of heat-shrink-tubing and slip it over one end of the broken wire, sliding it well away from the repair area. Solder the wires back together using resin-core solder. After the repair has cooled to the touch, slip the shrink tubing back down the wire to completely cover the repair. Use the soldering iron to heat the tubing, allowing it to shrink over the bare wires.
Perhaps the most difficult to troubleshoot, shorted wires can be frustrating to locate because they may only malfunction intermittently. It is important to have a good schematic of the wiring harness for your particular model Harley. This will greatly aid you in tracking down the culprit wire. Use an ohmmeter to measure continuity from one harness point to another, checking for shorts to ground. Sometimes it helps to jiggle the wires during measurement to watch for intermittent shorts.
Easily detected and repaired, burned-out bulbs can be replaced with a cross-tip screwdriver and a fresh bulb. If the brake light bulb burns out and a replacement is not readily available, a front turn signal light bulb may be pulled and substituted in it’s place. Many states do not require electronic turn signals in their motorcycle safety specifications, so going without a bulb for a short time in the turn signal may be preferable to a missing brake light.
All motorcycle batteries have an expected lifespan. On Harley Softail models, the battery is surrounded by the horse-shoe-shaped oil reservoir, further reducing it’s longevity. If you leave on the lights and drain your battery, however, you should be able to jump start it. Use a quality set of jumper cables and connect them between the motorcycle battery and a car battery. It is generally preferable to have the car turned off during this maneuver. While a running car may charge your bike battery faster, there is the risk of damaging your bike’s electrical system.
Components such as spark plugs, spark plug wires and coils go bad over time. Regular inspection and replacement of these components can keep you from breaking down on the roadside. When installing spark plugs, remember to properly gap them with a spark plug tool. Replacement with manufacturer-specified parts is generally the best way to go, unless you have a thorough knowledge of aftermarket components.