I replace the main wiring harness and all the sub-harnesses. I also replace all the electrical components. Since this bike sat for almost 25 years and the components and wiring were not in good shape, replacing it all should provide very good reliability.  You can see how I remove what was left of the original electrical system here.

• 61 BMW 1983 R80ST Remove Electrical System

Parts

Here are all the electrical system wiring and components I install. All of these were graciously donated by Euro MotoElectrics in support of my goal of auctioning this bike and donating all the proceeds to the Motorcycle Relief Project.

Part #	Description	Qty
61 11 1 244 096	WIRING HARNESS SECTOR CHASSIS, Main Harness	1
61 12 1 244 137	WIRING HARNESS TAIL LIGHT	1
61 12 1 244 138	WIRING HARNESS, BRAKE LIGHT SWITCH, REAR	1
61 13 1 244 090	WIRING HARNESS, BRAKE LIGHT SWITCH, FR	1
61 12 1 244 176	WIRE IGNITION COIL	1
61 12 1 243 523	WIRING TRANSMISSION-SWITCH	1
61 31 1 244 420	COMBINATION SWITCH LEFT	1
61 31 1 244 417	COMBINATION SWITCH RIGHT	1
61 31 1 244 070	STOP LIGHT SWITCH (from 09/80), Front Brake Switch	1
61 31 1 243 097	SWITCH, Transmission Neutral	1
61 31 1 243 414	OIL PRESSURE SWITCH – M12X1,5, Includes Washer	1
61 31 1 243 403	CLUTCH SWITCH	1
61 31 1 353 684	STOP LIGHT SWITCH, Rear Brake	1
61 31 1 373 588	MINI-RELAY, Headlight	1
61 36 1 389 105	RELAY, Starter Relay	1
62 14 1 243 581	LAMP – LEFT, Instrument Dash Turn Signal Indicator	1
62 14 1 243 582	LAMP – RIGHT, Instrument Dash Turn Signal Indicator	1
61 21 2 346 800	BATTERY, MAINTENANCE-FREE – 12V 19AH	1
61 21 1 233 028	RUBBER MOUNTING, Battery Box	4
61 21 1 243 562	ENSION STRAP, Battery Box	2

Here are the new engine electric components I install.

Part #	Description	Qty
12 11 2 413 906	IGNITION SENSOR-Refurbished By EME	1
12 14 2 325 284	IGNITION CONTROL UNIT	1
61 12 1 244 176	WIRE IGNITION COIL, ICU To Ignition Sensor	1
12 13 1 244 426	IGNITION COIL	1
12 12 1 243 453	IGNITION WIRE 5K OHM 40 CM, Set w/ 2 Wires	1
12 12 9 062 594	SPARK PLUG – BOSCH W7DC, NGK BP6ES Equivalent	2

Video

Here is a video summary showing how I install the electrical system.

VIDEO: 1983 BMW R80ST Install Electrical System

Bench Test Wiring And Components

I bench test the electrical wiring system before installing it. This lets me verify that almost every part of the wiring system is working, and if I find a problem, it’s easier to repair the problem before installing the main wiring harness and the electrical components on the bike. To start, I label all the connectors on the main wiring harness.

The main wiring harness comes with a wiring diagram and list of components,

The wiring diagram included with the main wiring harness indicates wire colors using abbreviations of the wire colors in German. That can be hard to comprehend. You can see what the abbreviations are for colors in this document.

• Electrical Basics
  • BMW Wire Colors

The Haynes manual includes color wiring diagrams which can be easier to read. That said, for wires with two colors, the stripe color can be hard to determine from the diagram, so cross-referencing the wire with the wiring diagram included with the main wiring harness helps identify the two colors. Here is a copy of the R80ST wiring diagram from the Haynes Manual. Click the picture to enlarge it.

NOTE:
When I mention two colors for a wire, the first is the solid color and the second is the stripe color.

Once I have the main wiring harness connections labeled, I install the sub-harnesses, relays, switches and lights. Here is a picture of the electrical system, except I didn’t include the ignition coil and voltage regulator.

Then, I use the new R80ST battery and attach the RED battery (+) terminal in the main wiring harness to the (+) terminal of the battery and attach the frame ground to the (-) battery terminal.

I attach the frame ground ring terminal and the battery (-) terminal. I also attach a jumper wire to terminal (85) with the BLACK wire on the headlight relay and connect it to the battery (-) terminal so the headlight relay has a ground and I can test the headlights.

NOTE:
On this bike, the headlights come on when the ignition is put in the ON position. But, they go out when you press the starter button. The wire on terminal (85) on the headlight relay goes to terminal (87) on the starter relay and from there the connection continues to the starter solenoid. This provides a ground path for the headlight relay except when the starter button is pushed. Then there is power on terminal (87) of the starter relay which flows back toward the headlight relay which means there is no voltage difference across the relay coil, so it closes turning off the headlight.

I start by turning the ignition switch to the PARK  position and verify that the running lights and instrument lights are working.

Then I turn the ignition switch to the ON position. I verify that the headlight, turn signals, horn, and front and rear brake light switches work.

Next, I press the left transmission neutral switch to verify that the neutral light in the tachometer goes out.

I use a volt meter to verify the starter relay is working. I test the starter relay output terminal (87) is on when the neutral switch is open and the right handlebar switch is closed and the starter button is pressed on the left handlebar combination switch.

This bench testing doesn’t verify that the starter motor and solenoid are working, but I bench tested those earlier.

• 12 BMW BMW R80ST Remove And Test Starter Motor

It also doesn’t verify if the ignition system and the charging systems are working. I’ll test those when I do the first engine start.

Install Headlight Bracket & Headlight Bucket

The top of the headlight bracket mounts on two shackles that fit under the fork tube top bolts.

The bottom of the headlight bracket mounts on two steel straps that attach to the bottom of the lower fork yolk and to the bottom of the headlight bracket.

 

I install the headlight bucket. It has two rubber washers; one fits against the headlight bucket and the other fits on the outside of the headlight ear of the headlight bracket. A bolt and large chrome flat washer secure the headlight bucket to the headlight ears.

Install Main Wiring Harness & Electrical Components

I start installing the main wiring harness starting from the front of the bike. I route it to the headlight, speedometer and tachometer, the ignition switch, the turn signal stalks and the dash turn signal indicator wires. Then I work my way toward the rear of the bike installing electrical components and connecting them to the main wiring harness.

The main wiring harness goes behind the headlight bracket. Toward the bottom there are tabs that I bend to hold the main wire harness in place.

Headlight

I insert the headlight socket and the BROWN and GREY-Black wires that go to the parking light inside the headlight shell. I insert the large rubber grommet into the hole in the bottom of the headlight shell.

I connect the socket to the three headlight terminals and the GREY-Black wire to the center terminal of the parking bulb socket and the BROWN ground wire to the outside terminal of the parking bulb socket.

I install the headlight reflector into the headlight shell and secure it with the tab and Phillips head screw that pulls the bottom of the headlight reflector tight against the headlight shell.

Temporarily Mount Speedometer & Tachometer

These attach to the top of the headlight bracket with two M5 studs that fit into holes in the headlight bracket. The speedometer is on the left and the tachometer is on the right as you sit on the bike. They fit into the dash. I’ll install them permanently when I install the handlebars and the instrument dash.

The speedometer has a bulb that illuminates the speedometer face. It pushes into a hole in the rear of the speedometer at the top.

The tachometer has all the indicator lights and connects to the main wiring harness with a round plug that has a raised half-circle in the middle that fits into a half-circle hole in the back of the tachometer so the plug connects to the correct pins.

Front Turn Signals

I push the turn signal wires–BLUE-Black (right) and BLUE–Red (left)–into the turn signal stalks behind the headlight bracket. I install the turn signal housings on the turn signal stalks. There is a notch in the stalks and a bracket inside the turn signal housing with a tab that fits into the notch locking the housing onto the stalk. The BROWN ground wire goes on the terminal attached to the side of the bulb and the wires go on the terminal attached to the center of the bulbs.

Ignition Switch & Turn Signal Indicators

I route the ignition switch wires so they are below the hole in the headlight bracket that the ignition switch fits into. I route the two sets of turn signal indicator wires so the BLUE-Black is on the right and the BLUE–Red is on the left side of the ignition switch as you sit on the bike.

I temporarily install the ignition switch so I can test the wiring system. The terminals on the back of the ignition are numbered and the wires go on the terminals as follows.

Terminal#   Wire Color
(30)             RED
(15)             GREEN
(54)             GREEN–Violet
(58)             GREY-Black

I’ll install the ignition switch and turn signal indicator wires later when I install the handlebars and the dash.

Horn

I install the horn on the bracket on the front frame cross tube. Unlike most BMW horns that install hanging down, the R80ST horn mounts at 90 degrees to frame bracket. The horn mounts with two thin steel straps on the back of the horn. These are important for making the horn vibrate so it is loud.
The BROWN–White and GREEN-Black wires attach to the terminals on the back of the horn.

Clutch And Front Brake Light Switches

I’ll install these with their sub-harnesses when I install the handlebars.

Ignition Coil

The ignition coil mounts on the right side of a bracket welded to the frame near the front of the bike. It attaches with two Allen head bolts with wave washers. I attach the GREEN–Blue pair of wires to the coil terminal near the frame and the pair of BLACK wires on the outside terminal.

Handlebar Multifunction Switch Sockets

The handlebar multifunction switch cables have a socket on the end that attach to sockets on the main wiring harness. The left handlebar multifunction switch cable has a RED and BLACK socket and the right cable has a WHITE socket which match the same color sockets on the main wiring harness. The main wiring harness sockets snap into holes in a bracket welded to the frame just above the coil. The front of the sockets has a ridge on the top and bottom of the socket and the rear of the socket has fingers on the top and bottom.

Ignition Control Unit

The ignition control unit (ICU) mounts on a heat sink which attaches to a bracket on the frame. The ICU has a metal base and two small plastic pins that fit in holes on the front of the heat sink. Two screws attach the ICU using the holes at the edges and screw into threaded holes in the heat sink.

Before I mount the ICU on the heat sink, I apply a heat transfer paste to the metal pad on the bottom of the ICU. This is important as the heat sink paste ensures that the ICU does not overheat. If it overheats, the ICU will stop working.

The heat sink attaches to the frame with two Allen bolts with wave washers.

The cable from the ignition trigger inside the engine has a wide connector that attaches to the bottom of the ICU and is secured by a wire bale. There is a white connector attached to wires (BLACK, BROWN, GREEN) from inside the engine that connects to a white socket on the main wiring harness with BLACK, BROWN, GREEN–Blue wires.

White Socket With BLACK and BLUE Wires

There is a white socket on the main wiring harness with a BLACK and a BLUE wire that attaches to a white socket with BLACK and BLUE wires that come from inside the engine. I orient the sockets to they are on the left side.

Voltage Regulator And Frame Ground

The voltage regulator is an Enduralast unit from Euro MotoElectrics. It is solid state and the charging voltage can be adjusted.

The voltage regulator attaches to a frame bracket to the rear of the ignition control unit. The cluster of BROWN frame ground wires with the ring terminal attach the voltage regulator mounting bolt nearest the frame.

The triangular black connector from the engine with the BLACK, BROWN & BLUE wires plugs into the bottom of the voltage regulator.

Headlight & Starter Relays

The headlight and starter relay sockets mount in a frame bracket to the rear of the voltage regulator bracket. The sockets have a tab and are secured with a screw that has a large flat washer. The relays plug into the top of the socket. The sockets install from the bottom of the bracket and are held in place with two ears on the sides of the socket. I label the top of the relays so I can easily tell which is the headlight and the starter relay.

Turn Signal Relay

The turn signal relay mounts on the same frame bracket as the headlight and starter relays. But, it mounts underneath the bracket. The original turn signal socket mounted in the screw hole next to the frame and the relay pointed toward the rear. The new wiring harness socket is longer so it won’t mount the same. I mount it in the outside screw hole and point the relay perpendicular to the frame. This shouldn’t make any difference.

Special Equipment Socket

This socket is painted blue. It mounts similarly to the way the handlebar multi-function switch sockets mount. However, It mounts from the bottom of the bracket. There was a black plastic cover that protected the pins from rain on the original socket and I install it on the new socket.

Fuse Box

The fuse box has two 8 amp fuses inside. It mounts at the end of the frame spine tube. There is a bracket that attaches to the fuse box. A hose clamp attaches the fuse box bracket to the bottom of the frame spine tube.

On the back of the fuse box are terminals on each side. I install the GREEN and GREY wires on the left side terminals. I install the GREEN-Black wire opposite the GREEN and the GREY-Black wire opposite the GREY wire. The GREEN and BLACK wires carry power from the battery and the black striped wires indicate that these carry power after the fuse.

Oil Pressure Switch & Transmission Neutral Switch

The oil pressure switch screws into a tapped hole on the lower left side of the engine block. The transmission neutral switch installs in the transmission, but I’m still rebuilding the transmission.

The transmission sub-harness has a BROWN–Green wire that goes on the terminal of the oil pressure switch. The BROWN-Black and BROWN wires go on the terminals of the transmission neutral switch. The BROWN wire with the ring terminal attaches to the transmission under the left bottom transmission mounting bolt. I’ll install the neutral switch wires when I install the transmission.

Rear Brake Light Switch

The rear brake light switch mounts on a bracket on the lower right of the frame. It is secured with two screws. The wires, GREEN-Black and GREEN–Red, thread through a rubber cover that protects the switch from water. The wires fit into holes in the switch body and are secured with two set screws. The sub-harness wires connect to a plug on the end of the main wiring harness.

Install Rear Sub-Frame

I install the rear subframe so I can install the rear turn signals. It attaches to the frame with four bolts. The top right leg of the rear sub-frame attaches with a bolt that screws into a tapped hole. The other three bolts have washers and nuts. I torque all the bolts to 16 Ft-Lbs.

Install Rear Turn Signals

The rear turn signal stalks mount to the rear of the sub-frame. There is a hole next to the mounting bolt for the turn signal wires in the rear wiring sub-harness. I attach the rear wiring sub-harness to the plug at the end of the main wiring harness. Then I push the wires through the holes in the turn signal stalks; BLUE-Black wire is right side and BLUE–Red wire is left side.

The rear turn signal housing mounts to the stalk and the wires attach to the turn signal reflector the same as on the front turn signals. The lens has the same “TOP” mark as on the front.

Install Rear Tail Light

The rear tail light housing mounts on the rear fender, but that is still at the painters, so I can’t mount the rear tail light. But I wire it up so I can test it.

The rear bulb has two filaments, one for the park/running light and the other for the brake light. On the back of the reflector, the terminals are labeled (54) for the brake light and (58) for the park/running light. The brake light wire is GREEN–Red and the park/running light wire is GREY-Black. The BROWN ground wire attaches to the strap on the outside of the bulb.

Install Battery Box And Battery

The battery box mounts in the frame on four rubber bushings with studs that act as vibration dampers. Each stud has a nut and wave washer. Two of the vibration dampers mount on a bracket on the lower frame cross tube and the other two mount on the vertical frame tubes.

The battery mounts in the battery box with two rubber straps that attach to brackets on the bottom rear and top front of the battery box.

I attach the cable from the starter motor and the wire from the main wiring harness, both of which have RED markings on the ends, to the battery (+) terminal. I install the battery ground cable to the battery (-) terminal using the ring terminal with the 90 degree bend. The other end of the ground cable attaches to the transmission using the speedometer drive bolt, but I haven’t installed the transmission yet, so I use a jumper wire to attach the end of the ground cable to the transmission stud on the rear of the engine block. I also attach the ring terminal with the BROWN wire from the neutral and oil pressure switch sub-harness to the the transmission mounting stud so I can test the neutral switch.

Test Electrical System

I temporarily connect the ignition switch so I can test the electrical system. I test the PARK and ON positions of the ignition switch and the kill switch. I test the horn, high beam and high beam flasher. I verify that the indicator bulbs in the tachometer work. I test the brake lights.  Everything works. 🙂

Here is how the bike looks with the electrical system installed.

Revisions

2022-12-17  Add explanation of getting headlight relay to work for wiring bench test.