I’ve removed the tank, seat, fairing and rear fender assembly. That exposes all the electrical system components except for the charging system (alternator, diode board and associated wiring), the ignition “bean can” under the front engine cover and the starter motor and starter solenoid under the top engine cover.

Video Tour of the Electrical System

It’s hard to see where wires and cables go in pictures. I shot some video of these details as I disassembled the electrical system. The video highlights what’s in this document.

VIDEO: Removing the Electrical Wiring Harnesses and Components

Wiring Sub-harnesses

The design of the wiring system employs a number of sub-harnesses that plug into the main wiring harness using connectors. The sub-harnesses include:

• Fairing
• Handlebar Clutch Switch
• Front Brake Light Switch
• Ignition Module
• Rear Brake Light Switch
• Oil Pressure Sender and Neutral Switch
• Rear Sub-frame

Fairing Sub-harness Connector

The fairing sub-harness connector is zip tied to the left upper leg of the upper fairing bracket. The wires in this sub-harness go to the front turn signals, clock and volt meter. See the section ” ” to learn how to remove this sub-harness.

Handlebar Clutch Switch Sub-harness Connector

This connector is zip tied against the left side of the frame tube near where the left disk steel brake line comes out of the front disk brake line manifold that the ignition module mounts on top of.

The clutch switch lets you start the engine when the transmission is in gear by pulling in the clutch lever. The clutch switch is mounted inside the left control perch.

Front Brake Light Switch Sub-harness Connector

The front brake light switch sub-harness connector is next to the clutch switch connector near the left brake line from the front disk brake line manifold.

Ignition Control Unit Sub-harness Connectors

The ignition control unit sub-harness has two connectors; a special one that connects to the ignition control unit on top of the brake line manifold (aka, splitter) and a white connector on the right side of the frame spine tube with a GREEN–Blue, BLACK and BROWN wire.

One side of the white connector goes to the ignition control unit mounted on the top of the front disk brake line manifold while the wires in the other side of the white connector go inside the engine via a hole in the top of the inner timing cover to the ignition sensor, aka the “bean can” that is inside the front engine cover.

I remove the ignition control unit and the special connector when I remove the brake system and you can see how to do that here:

• Remove Front Brake Line Splitter-Manifold

Rear Brake Light Switch Sub-harness Connector

The connector for this harness is on the right side of the frame spine tube near the back of the right coil.

Oil Pressure Sender & Neutral Switch Sub-harness Connector

The connector for the oil pressure sender & neutral switch sub-harness is on the left side down tube next to the battery.

Rear Sub-frame Sub-harness Connector

The rear sub-frame sub-harness connector is tied to the left tube of the rear sub-frame.

Remove Rear Sub-harness

I removed the rear sub-harness when I removed the rear fender assembly. This sub-harness connects to the tail light (parking light and brake light) and the rear turn signals. You can see how I removed this sub-harness here.

• Remove Tail Light Housing
• Remove Turn Signals

Remove Rear Brake Light Switch and Sub-harness

The rear brake light sub-harness is secured to the rear brake light switch with two screws underneath the rubber cover on the top of the switch. There is almost no clearance between the top of the cover the bottom of the muffler bracket so I struggled to get the rubber cover off.

Removing the rear brake light switch was also a bit of a challenge. There are two screws that secure it to a tab on the inside of the right muffler bracket.

The inside Phillips head screw is easy to get to.

But the rear screw that secures it to the tab on the muffler bracket is accessed from a hole in the top of the muffler bracket. There was so much crud and gunk–plus it’s dark in there :-)–that it is hard to see the the Phillips head screw. And, the rear sub-frame brace runs right next to the hole so getting a screw driver in the hole and into the Phillips head screw was difficult. I didn’t want to strip the head of that screw. Finally, I used my stubby Phillips head screw driver and got that screw out.

Remove Oil Pressure & Neutral Switch Sub-harness

This harness connects to the top of the oil pressure sender on the left side of the engine block near the lower frame tube.

It also has a BROWN ground wire that attaches to the left lower transmission Allan bolt. I can just fit an Allan key wrench on the bolt and loosen it. Then I remove the wrench and use my fingers to get it out. It’s a very tight fit.

There are two wires that attach to the neutral switch. I use needle nose pliers to pull the leads off the neutral switch terminals.

Remove Auxiliary Power Socket and Sub-harness

The auxiliary socket someone added has a bracket that attaches to the left top shock bolt. I remove the nut to get the bracket and wiring sub-harness off.

Remove Starter Relay

The starter relay attaches to the left side of the frame spine. The relay plugs into a socket and the wires that go into the bottom of the socket are in the main wiring harness.

The bottom of the relay has the terminal numbers stamped next to the terminals.

The top of the relay has the Bosch part number (0 332 014 118) and on one side is a diagram of what the terminals connect to inside the relay.

• Terminal (86) is power into the relay,
• Terminal (85) is the relay ground which goes to the starter button,
• Terminal (30) is the switched power in from the battery
• Terminal (87) has two spades and is the switched power out of the relay to the starter solenoid

The relay socket attaches to a bracket on the frame with a Phillips head screw with a wave washer.

There is one large RED wire going to one spade of Terminal (87). This wire is part of  the cable with the large BLACK wire that goes to the battery (+) terminal. The other end of the battery (+) cable goes to the starter solenoid under the top black engine cover. Rather than remove the top engine cover and remove the battery (+) cable from the starter solenoid, and since I wanted to see how corroded the spade was, I removed the large RED wire from the starter relay using a small jewelers screw driver to flatten the tab that holds the terminal in the relay plug.

The spade terminal is not too bad. I’ll clean all the wiring harness terminals before I put the harness back into the bike.

Since I flattened the prong on the spade terminal with the jewelers screw driver, I bend it back so when I insert the spade back into the plug, it will stay seated.

WARNING
The retaining pin can be bent, but it is possible it will break off. In that case I would remove the broken spade terminal and solder a new one on the wire. For this reason, you may want to remove the battery (+) cable from the starter relay when removing the main wiring harness. I plan to clean all the terminals which will require me to remove them from the starter relay plug.

Behind the stater relay was a connector with a BLUE and a BLACK wire. I believe this connector is supposed to be underneath the starter relay so it is easy to get to.

The wiring diagram in the picture below shows this connector.

The BLUE wire goes to the (D+) terminal of the voltage regulator and comes from the charging light indicator in the instrument cluster while the BLACK wire comes from terminal (30) of the starter relay and goes to the starter solenoid under the top engine cover.

Remove Coils

The two coils attach to a bracket on the frame spine.

The left coil has the BROWN frame ground wire attached to the front bracket bolt. This bike has an optional auxiliary power socket and it’s BLACK ground wire is attached to the other bolt.

I remove the spark plug cable from the coil.

The left coil has two wires attached, a GREEN–Blue on the upper terminal and a BLACK on the lower terminal that goes to the lower terminal on the right coil.

The right coil has two BLACK wires on the upper terminal. The lower terminal has the other end of the short BLACK wire from the left coil’s lower terminal.

Remove Voltage Regulator

The voltage regulator mounts to a tab on the right side of the frame spine tube under the front brake line manifold. It is attached with two screws and wave washers.

NOTE:
I opened the can the regulator fits inside of earlier as part of my investigation about a flickering charge indicator light. The black tape is 3M waterproof tape.

The wires go into the bottom of the regulator with a triangular plug that has the terminal numbers marked on the bottom of the plug.

Remove Fairing Sub-harness

I removed the fairing before I removed the fairing sub-harness. It is easy to remove the clock and volt meter connections when the dash is removed, which is what I did when I removed the fairing, as shown here.

• Remove Volt Meter, Clock & Ignition Switch From Dash

But it is possible to remove them with the dash attached to the fairing. Access to these terminals is possible if you remove the parking light assembly and the headlight tunnel with the glass cover in front of the headlight. That said, putting the sub-harness connectors back onto the clock and volt meter terminals requires a bit of double jointed dexterity 🙂

Remove Headlight

Before I can remove the headlight, I removed the windscreen, mirrors, dash and the fairing, and you can see how I did that here:

• 46 BMW 1983 R100RS Remove Fairing, Dash, Volt Meter, Clock, Ignition Switch

Now, I can remove the headlight shell from the upper fairing bracket.

There is a Phillip head screw on the bottom of the headlight chrome ring that holds in on the shell.

After I remove it, the headlight lens and chrome ring come off the shell. The lens is still connected by the headlight wiring connector.

I remove the headlight lens from the connector so I can get a clear view of the wiring inside the headlight shell.

I was inside the headlight shell before and labeled the turn signal relay and the headlight relay. Note in the back of the shell is a terminal board, or punch down block that almost all the wires inside connect to. The board is organized in sections with a color code that matches the colors on the insulation of the wires. This makes it much easier to find wires and to install them without getting confused.

I make note of the damaged grommet that isn’t sealing the left side controls cable and will let water inside the headlight shell.

In use a 27 mm socket to remove the chrome retaining nut on the left side of the headlight shell.

There is a sandwich of a metal washer a rubber grommet and another metal washer underneath the chrome retaining nut.

I remove the chrome 13 mm bolt on the right side of the headlight shell.

There is large chrome washer a rubber grommet behind the 13 mm bolt.

I more the headlight shell forward on the right side and retrieve a second rubber grommet between the headlight ear and the shell.

I pull the right side of the headlight shell farther out so I can slide the threaded plug on the left side of the shell out of the headlight ear.

When I pull the left plug out of the headlight ear, I retrieve another sandwich of a metal washer, rubber grommet and metal washer.

I use a piece of garden green wire to keep all the left side headlight shell mounting hardware in the correct order.

Remove Horns

This bike has dual Fiam horns. Earlier models with the Fiam horns had a horn relay, but it is not used on the 1983 model.

Each horn has a black wire to a single terminal located on the inside of the horn housing. The mounting bolt creates the ground path back to the battery (-) terminal.

The horns mount to tabs on the front down tubes of the frame. There is black plastic vanity cover over the bolt heads which is also used on the front rear sub-frame mounting nuts. I remove the plastic vanity cover and then the horn brackets.

Remove Handlebar Combination Switches

Since I’m going to keep the main harness attached to the terminal board in the headlight shell, I remove the left and right handlebar combination switches that are connected to the headlight shell.

Remove Instrument Cluster Rubber Connector

This large rubber connector houses 12 pins and attaches to the back side of the instrument cluster with a single, small Phillips screw. I loosen the screw until I am able to unplug the rubber connector from the instrument cluster and leave the screw in the connector.

Remove Main Harness

With all the components and wiring sub-harnesses disconnected from the main wiring harness and the headlight removed from the top fairing bracket, I can remove the main wiring harness.

But before I remove the main wiring harness, I label the branches with tape so it will be easy to attach them to the correct component or sub-harness when I install the electrical system.

I pull the rear end of the harness through the gap between the frame upper spine tube and the short lower section to the right side of the bike. Then I pull the harness out from the front of the bike threading it between the two down tubes that attach to the steering head.

VIDEO: Pulling The Main Wire Harness Out of The Bike

Revisions

2019-04-10 Added Horn Section
2019-12-04 Cleaned Up Ignition Terminology and Edits.