Wire A Harley Tachometer

Wire a Harley Davidson tachometer in a few steps and with some basic tools.

Harley Davidson motorcycles have a nearly flawless reputation when it comes to customer loyalty, pride and satisfaction. Every conceivable component, accessory and option can be purchased for Harley motorcycles, including a vast array of add-on electronics. Unfortunately, some Harley Davidson motorcycles do not come equipped with a tachometer as standard equipment for the instrument cluster. That has not stopped Harley enthusiasts from purchasing Harley tachometers for their motorcycles. Many tachometer kits come ready to install. Knowing the proper wiring procedure can help the motorcycle owner complete the task in a short time with a few basic tools.


1. Place the motorcycle in a well-lighted area. Raise it up on its utility kickstand, if it is equipped with one. Refer to your owner’s manual for the battery location; it could be under the seat, out in the open or behind a side cover. Remove the bolts to whichever component you need to take off with a socket and wrench. Disconnect the negative battery cable with a small socket and wrench. Turn the gas valve to the “Off” position. Loosen the fuel line clamp with a screwdriver and pull the hose free.

2. Locate the mounting bolts for the gas tank. Loosen and remove the bolts with the proper size socket and wrench. Pull the tank up and disconnect any wire jacks belonging to inset tank gauges. Set the tank down. Open the kit and assemble the mounting hardware. Most tachometers have a convenient handlebar or triple tree clamps.

3. Set the tachometer clamps around the handlebar. Insert the through-bolts and place the lock washers and nuts on the bolt threads. Tighten the bolts with a socket and wrench. Adjust the tachometer and tighten the swivel adjusting bolt with a socket and wrench. Loosen and remove the screws to the headlight shell with a screwdriver. Look at the tachometer wires; one will be marked for the power and is usually red. Another wire will be green for the magneto or coil connection and the black wire has a ground designation.

4. Connect the negative cable backup to the battery with a socket and wrench. Turn the ignition key to the “On” position. Locate the hot wire inside the headlight case by using a test light to probe the wire while you turn the ignition key on and off. The test light will illuminate on the proper hot wire. After identifying the hot wire, remove the negative battery cable with a socket and wrench. Route the positive red wire on the tachometer down to the headlight casing and push it through the grommet hole in the headlight case.

5. Cut the red wire to the proper length with wire strippers. Make sure you have left enough wire to tape to the headlight wire loom or tie-strap it to the frame. Join the tachometer positive wire to the headlight positive wire with a snap wire connector by aligning both wires together and snapping the connector over them with your fingers. Look for a ground bolt or screw inside the headlight case and remove it with a socket or screwdriver.

6. Run the tachometer ground wire through the headlight case grommet. Cut off the excess wire with the wire strippers. Crimp a wire eyelet on the ground wire with the wire strippers and place the eyelet over the bolt or screw. Tighten the ground bolt or screw with a socket or screwdriver. Replace the headlight shell. Screw the headlight shell screws back in with the screwdriver.

7. Take the green tachometer wire and route it along the top support frame, next to any other existing wire loom. Route the wire to the magneto location, or to the coil, if so equipped. Leave enough wire to connect to the “trigger” side or negative post on the magneto. Do the same for the negative terminal for a coil. Cut off the excess wire. Crimp a wire eyelet on the green wire with the wire strippers. Unscrew the nut on the magneto or coil and place the eyelet over it. Tighten the nut back down with a socket.

8. Look at your wiring route. Secure the tachometer wires to existing looms or to the frame parts with black electrical tape and tie straps. Tape them neatly, and if possible, tuck them on the underside of any larger loom. Place the gas tank back on its mount and start securing the bolts by hand. Tighten the gas tank bolts with a socket and wrench. Push the fuel line back on the tank nozzle and tighten the hose clamp with a screwdriver. Turn on the gas tank valve.

9. Reconnect the negative battery cable with an end wrench. Replace the seat or side case if you had to remove it to access the battery. Tighten the bolts with a socket and wrench. Test ride the motorcycle and note the operation of the tachometer.