How to Wire a Motorcycle Headlight

by Chris Gilliland
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Converting an off-road motorcycle for street duty requires some extensive electrical work to add on the necessary lighting equipment, with the headlight taking the highest priority. However, many of the dirt bikes that can be converted don't provide the necessary amenities to make headlight installation a plug-and-play affair, requiring its owner to locate the motorcycle's ignition power wire on their own. Once located, a handlebar-mounted control switch diverts power to either the headlight's high or low-beam. This project requires basic wiring skills and an extensive knowledge of your motorcycle's chassis and electrical system to complete.

Step 1

Remove the motorcycle's fuel tank, seat and any bodywork required to access the motorcycle's frame and electrical system.

Step 2

Separate the headlight control switch's upper and lower housings, using a Phillips screwdriver to unscrew the pair of bolts from the bottom of the switch housing. Place both halves of the headlight control switch housing over the handlebar and tighten both bolts with a Phillips screwdriver. Route the headlight control switch's wiring loom through the front for and to the motorcycle's frame.

Step 3

Locate the ignition wire on the ignition switch's wiring loom with a multimeter set to read the DC (direct current) voltage scale. Press the multimeter's red positive probe onto the ignition switch's wires, pushing into the wire's rubber insulation. Place the black negative probe onto the motorcycle's frame to provide a ground connection. Turn the ignition switch to the On position. Test each wire until a voltage reading is indicated by the multimeter. The ignition wire will only provide a voltage reading with the ignition switch set to the On position.

Step 4

Cut a length of yellow electrical wire with wire cutters to serve as the headlight's power wire. The wire must be long enough to connect the headlight control switch's positive wire to the motorcycle's ignition wire. Splice one end of the wire onto the ignition wire with a T-tap connector.

Step 5

Route the power wire to the headlight control switch. Connect the power wire to the switch's positive wire with a butt connector. Crimp both ends of the butt connector with a wire crimping tool to secure the wires in place.

Step 6

Cut a pair of red electrical wires with wire cutters–one wire for low-beam, the other for high-beam--to extend from the headlight control switch to the headlight's bulb socket. Join the extended wires to the switch's high and low-beam wires using butt connectors. Route the extended wires to the headlight socket. Join the extended high and low-beam wires to the socket's high and low-beam wires with butt connectors.

Step 7

Cut a length of black electrical wire with wire cutters. This wire will serve as the headlight's ground wire. Cut the wire long enough to reach the battery's negative terminal. Connect the headlight socket's ground wire to the extended ground wire with a butt connector. Strip off a quarter-inch of insulation from the remaining end with a wire stripping tool. Crimp a terminal connector onto the exposed wire using a crimping tool. Connect the terminal to the battery's negative terminal with a Phillips screwdriver.

Step 8

Turn the ignition switch on and cycle between high- and low-beam to ensure the headlight operates properly. Check all wiring and ground connections if the headlight does not illuminate.

Step 9

Secure the headlight's wiring to the frame with nylon cable ties. Reassemble the motorcycle's bodywork, seat and fuel tank.

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