I show how I remove the main wiring, various sub-harness’, instruments and the electrical components in this write-up.

• 61 BMW 1977 R100RS Remove Wiring Harness, Instruments & Electrical Components

Based on the amount of oxidation and the cracks in the outer sheath, not to mention the age of the wiring harness, it needs to be refurbished or replaced. That said, the 1977 R100RS main wire harness (part#  61 11 1 243 222) is a one year only harness and is no longer available from BMW. I did find one source for the main wire harness, Todd Millican, at “Brits and Beemers“, but at a quote of $500 (which is not unreasonable IMHO due to the labor required to make a quality harness which is what Todd does) I can afford to invest a lot of my time at my current hourly rate [about $0.00 if I don’t count the beer and who counts the beer 🙂 ] and see if I can’t get it back into shape. The work I did includes:

• Remove pins from and terminals from all connectors, clean and reinstall.
• Repair tears in the outer black protective sheath of the harness’.
• Test the horns (they still worked). Clean and repaint them to freshen them up.
• Replace damaged spade terminals with new ones.
• Replace torn/missing rubber sleeves over the outer sheath where individual wires and branches exit the harness with shrink tubing.
• Clean outer sheath and all exposed wire insulation.
• Replace the starter and horn relays, voltage regulator, the oil pressure switch, and the neutral switch.
• Install electrical components
• Install headlight with main harness and connect to electrical components
• Install fairing & dash instrument sub-harness and connect to instruments, ignition switch, turn signals and parking light
• Install rear sub-harness, tail light and turn signals

The inside of the headlight shell showed no rust and all the internal connections are clean and not oxidized which is welcome news. That’s one reason I decided not to replace the harness and invest to refurbish the wiring.

The VDO oil pressure and temperature gauges have a sub-harness the goes to contacts inside the headlight shell. The harness had been cut and I don’t plan to use the gauges at the moment, so I remove these wires from the terminal board inside the headlight shell.

Resources

There are several resources on Bob Fleischer’s site about airhead wiring:

• Metric & American Wires, Colors, Bosch wire & Connection Codes, Sources & Wiring, Schematic Diagrams, etc.
• Electrical Hints, Problems, Fixes
• Basic Electricity 101+
• Miscellaneous Electrical

I have both the Haynes and Clymer manuals and both have wiring diagrams. Of the two, I prefer the Haynes and it’s color wiring diagrams that are easier to read. That said, there are differences in both manuals from how the wiring was actually done inside the headlight shell. By comparing the connections in the headlight shell with the two diagrams, I can see what wires go where. I did that to confirm no one had futzed with the wiring inside the headlight shell. It looked to me that the main harness and handle bar switch harness connections inside the head light shell go where they ought to.

Parts

Here are the parts I installed for this work. I sourced most of them from Euro Motoelectrics and show their part numbers. The BMW part number is in { } in the description. Due to the age and condition of the horn and starter relays, and the voltage regulator, I chose to replace them. The oil pressure sender had been replaced by a VDO oil pressure gauge and sender which I currently don’t plan to use so I got a new oil pressure switch I got a new neutral switch for the transmission. I replaced the (+) battery cable when I refurbished the starter motor and have a new (-) ground cable. Electrical reliability should be improved with the refurbished wire harness’ and new components.

Part #	Description	Qty
BCK-475216	Battery Cable Kit (4 Gauge) – BMW R Airhead / Negative {BMW # 61 12 1 244 475} Positive {BMW#  61 12 1 243 216 or 61 12 1 243 874}	1
BAT-12V30	Battery 12V/30AH – WestCo AGM {BMW# 61 21 1 459 650]	1
NPS-097	Neutral Position Switch – BMW R Airhead {BMW# 61 31 1 243 097}	1
61 31 1 355 262	GASKET RING – A 12,2 X 20-AL	1
OPS-414	Oil Pressure Switch-BMW R Airhead {BMW# 61 31 1 243 414}	1
OPS-414CW	Oil Pressure Switch Crush Washer {BMW #61 31 1 243 414, 61 31 1 354 274, 12 61 1 277 642}	1
REL-588	MINI-RELAY (to 09/78) Horn Relay w/ resistor BOSCH {BMW# 61 31 1 373 588}	1
REL-207	Relay-Starter BMW R Airhead / Bosch {BMW# 61 31 1 243 207}	1
EDL1-ALTKIT 107	INCLUDED IN KIT: BMW Voltage Regulator: {BMW# 12 32 1 244 409}	1

Tools

Nitro Tape – I got this from Motion Pro. It is a thin silicone tape that molds to itself. I like it for repairing tears in the outer protective sheath around a bundle of wires.

Cleaning Solution – I use a white vinegar with salt solution to remove corrosion from the terminals. After soaking for a few minutes, I dip the terminals in a solution of baking soda to neutralize the vinegar. I brush the terminals with a brass brush to remove the loosened crud.

Round Male Pin Removal Tool – This tool compresses the prong on round male terminals so they can be removed from a plug. I got it from Mouser Electronics, Inc (Part# 571-4656441)

Female Spade Terminal Removal-Screw Driver & Pick – I use a small, thin blade screwdriver and/or a pick to compress the prong on these terminals so they can be removed from the sockets the horn and starter relay plug into and various other terminals that had a plastic housing around the terminals.

Wire Strip & Terminal Crimp Tool – This tool strips insulation without nicking the wire and crimps the end of a female or male spade terminal. I also solder them.

Soldering Iron, Flux, Solder – These are used to solder a new terminal on a wire. Even though the solder has some flux in it, I like to add flux to the joint and heat it up before applying the solder to ensure a good clean solder joint.

Multi-Meter – I use it to test for continuity, to trace a wire in a harness, and to be sure the resistance of the wire is low to prove the wire is not broken somewhere in the harness. I have collected several over the years including the expensive Fluke meter which was a gift 🙂

Clean & Repair Wiring Harness’ & Terminals

The terminal connections and the plug terminals all need cleaning. Many of  them are green with corrosion.

Remove Terminals From Plugs

I use a small, thin blade screw driver and a pick to flatten the tab holding the female spade terminals in the horn and starter relay so I can remove them. Some of the connectors with one or two wires have a plastic cap and a pick works to flatten the tab on the terminals without cracking the plastic. The rear sub-harness uses round pin terminals and I use a special tool for removing them. It flattens the two tabs on the side of the pin so it can be removed from the plastic plug.

Cleaning Terminals

I dip the terminals in a white vinegar and salt solution for 3 to 5 minutes. This dissolves much of the corrosion off the terminals. Then I put them into a baking soda solution to neutralize the acetic acid in the vinegar. Then I use a brass wire brush to polish each terminal. It takes time but the corrosion is gone.

I use a small round file to polish the inside of the round edges of the female spade terminals. The end of the file is serrated and works as well.

The tab on the side of the spade terminals and round pin terminals gets flattened to remove the terminal. I use the small pick and screw driver to gently pry the tab so it is exposed and will lock the terminal in the slot of the plug.

Remove & Reattach Rubber Cover From 90 Degree Terminals

These female terminals have a rubber sleeve that wraps around the terminal. These type of terminal are used for the wires that plug into the ignition switch and other connections. I slip a thin blade screw driver under the edge of the rubber where the two ends are sealed and carefully peel the ends apart.

After I clean them, I reattach the rubber boots and stick the ends back together using 3M “Gorilla Snot”.

Replace Damaged Terminals

One of the terminals to the starter relay got mangled when I was removing it and the terminal for the oil pressure switch had been replaced with a ring terminal to attach it to the VDO pressure gauge.

I illustrate the procedure with the oil pressure switch spade terminal. The difference for the starter relay terminal is the omission of the shrink tubing over the crimped end of the terminal.

I cut the old terminals off and install new female spade terminals.

I strip the insulation using the stripper-crimper so there is about 1/8 inch of bare wire. I thread a smaller diameter shrink tube over the wire that I will heat to shrink around the wire and the where I crimp it.

Then I crimp the terminal in two places, over the insulation and over the bare wire. I use needle nose pliers to shape the two tabs on the terminal so they are rounded and the ends centered over the wire and use the crimper anvil to bend them securely around the insulation and the wire.

Then I solder the bare wire to the terminal to ensure a good connection. I put some flux on the wire and heat it with the soldering iron to clean the wire,

I slip the small diameter shrink tube over the terminal end where I crimped the wire and heat it. Then I slip a larger diameter shrink tube over the spade end of the terminal so it covers all of the spade and then heat it to shrink it around the spade.

Repair Outer Sheath

The outer sheath on the main and a couple of the sub-harnesses have tears. Also, several of the rubber seals installed where branches and wires exit the harness are degraded and torn.

I use Motion Pro “Nitro Tape” to repair the tears in the outer sheath. The tape fuses to itself when stretched. I cut a piece and then tightly wrap it around the outer sheath starting about 1 inch before the tear and sending 1 inch after. I use two layers. I use it the same way to replace torn rubber seals where large branches exit the main harness.

There is a rubber sleeve wherever a branch or wire exits the harness bundle. Many of these have torn or come loose. I use shrink tubing and nitro tape to replace these.

Install New Turn Signal and Parking Light Rubber Boots

The original boots have lost their elasticity and are torn so I replace them.

They were secured with rubber sleeves. I use three pieces of shrink tubing of increasing diameter to secure the new rubber boots to the wiring harness.

Test Ignition Switch

The ignition switch wires come out of the back of the headlight shell and connect to terminals on the back of the ignition switch that mounts in the dash.

Here is a short video showing how I test the ignition switch.

VIDEO: Testing The Ignition Switch

Install Main Harness Terminals into Horn & Starter Relay Sockets

It’s easier to install the wires from the main harness that plug into the horn and starter relay sockets with the harness out of the bike. There are other wires that go into these sockets that come from the (+) battery cable and the alternator and I’ll put those into the sockets after I thread the main harness into the frame.

The bottom of each relay has numbers next to the pins that correspond to the numbers in the wiring diagram.

 

I also drew diagrams of where the wires were plugged into bottom of the sockets when I removed them. But, the red insulation had weathered to brown and that confused me when I looked at the wiring diagram colors when it came time to reassemble the wiring into the relay sockets. Then I discovered the insulation had faded and the mystery was solved. 🙂

Each relay can plug in only one way into the socket. I put each relay loosely into it’s socket, turn it upside down and then remove the relays with the pins and numbers pointing up. This provides a good way to make sure I get the correct terminal plugged into the correct bay of each socket.

I start with the starter relay and plug the double red wire terminal into bay 87, then the double green-blue wire into bay 86 and the blue-yellow wire into bay 85.

Now I plug wires into the horn relay starting with the two red wires into bay 30 and the two brown wires into bay 85 and the brown-white into bay 86. The two black wires go the each horn and plugs into bay 87.

Here is where the wires from the main harness go into each socket; the starter relay socket is on the left and the horn relay socket is on the right.

Here is the assembly ready to thread into the frame. The blue wire with the white plastic connector plugs into a companion blue wire from the alternator harness.

Install Main Wire Harness in Frame

I did not remove the main wiring harness connections from the headlight shell other than one by one to verify that the contacts were clean and in good condition. So I need to install the headlight shell and then route the harness along the frame spine tube. To do that, I install the top fairing bracket which has the ears the headlight shell mounts to. Unlike the “naked” or “S” model bikes that have headlight ears that fit on the top of the fork tubes between the top brace and lower triple clamp, the RS fairing bracket supports the headlight.

Install Top Fairing Bracket

There are two bolts that thread into two tapped holes in the steering stem that secure the upper fairing bracket to the frame.

Install Headlight Shell

The ignition switch for the RS is in the dash instead of in the left side of the headlight shell as is the case for naked and “S” bikes. Consequently, a threaded plug is installed in the left side of the headlight shell to take the place of the ignition switch and its threads.

A rubber gasket and metal washer go on the plug so they fit against the inside of the headlight ear of the upper fairing bracket.

The right side of the headlight ear has a large metal plate that is tapped for a mounting bolt.

Another rubber gasket goes between it and the upper fairing bracket ear.

I install the headlight shell by inserting the left plug into the ear of the upper fairing bracket and carefully pulling the right ear outward until the right side of the headlight shell slips inside the ear being careful not to scratch the ear nor the headlight shell and keeping the rubber gasket between the ear and the metal plate.

Here is the hardware that goes on the outside of the right side ear.

I leave the bolt loose until I get the left side hardware installed. It includes another rubber gasket that fits against the outside of the left ear and two metal washers and a chrome nut. One washer is flat and goes against the rubber gasket and the second is wavy and goes against the chrome nut.

I snug up the right bolt and left chrome nut with the headlight approximately centered in the two ears. I’ll adjust the left-to-right and up and down angle of the headlight to align the headlight later.

Here is the headlight shell mounted in the ears of the upper fairing bracket with the left and right handlebar switches showing.

I route the main harness and the various branches starting from the front of the bike.

Left Handle Bar Clutch Switch Plug

This is the branch that connects to the left handlebar clutch switch.

Front Brake Master Cylinder Wires

I route the branches that go to the front brake master cylinder and connect them. There are two wires that go to the fluid reservoir level switch in the cap and the two wires that go to the front brake light switch on the front of the master cylinder.

I previously installed all the main harness wires into the horn and stater relay plugs and push that through the gap between the frame front down tubes.

Install Horn and Starter Relays

I add the missing wires to the relay sockets that come from the (+) battery cable and the alternator.

Then I install the two wires that come from the diode board and starter solenoid via the wire harness sticking out of the top of the engine behind the front engine cover.

The black wire comes from the starter solenoid and goes to terminal 30 on the starter relay.

The blue wire comes from the diode board and connects to the main harness blue wire via the white plastic plug.

Install Voltage Regulator

I bought an EME electronic voltage regulator and install it where the original regulator went. It mounts to the tab on the right side of the spine tube with two Allan bolts. The three prong plug from the alternator wiring harness plugs into the bottom. There is a small white dial on the bottom that adjusts the maximum charging voltage, but I leave it at it’s original setting.

Install Dyna III Electronic Ignition Module

The bike had a Dyna III electronic ignition with the “brown” dual plug coils. Due to the corrosion inside the points housing and damage to the aluminum sleeve that has the magnets for the hall effect sensor that acts as the points, I replaced it Dyan III ignition system with a new one. The dual plug coils did not appear to be damaged so I will use them.

You can read about how I installed the points and adjusted the advance to compensate for the dual plug heads here:

• 12 BMW 1977 R100RS Changes To Ignition For Dual Plug Heads
• 12 BMW 1977 R100RS Install Dyna III Electronic Ignition-Refurbish Automatic Timing Unit (ATU)

I repainted the coil brackets and then installed them and the coils on the frame. Note the brackets have a bend in them and I show the correct orientation of the bracket on the frame and how the coils bolt to the bracket.

I removed the spade terminals from the coils to clean them. Note that the clearance between the bracket bolt and the spade terminal bolt is so limited that the spade terminal bolt has to be installed first and then the bracket bolt inserted just enough to thread the nut on the end and then holding the bracket bolt nut while the head of the bolt is tightened.

The other bracket bolt is easy to install.

I clean the paint off the coil bracket around the holes the Allan head bolts go through to mount the brackets. I will attach ground wires to the bolts and want to get a solid ground.

I attach the spade terminal with several brown ground wires to the left front bolt and use my ohm meter to test for a solid ground.

The coils are connected in series with a short, black jumper wire that goes between the two inner spade terminals on the coils.

The amplifier has two sets of wires: a white and red pair that plug into the leads coming from the points and a brown, red and black set that go to the coils. The red that goes to the points has a micro plug and can’t be confused with the red that goes to the coils which has a female spade terminal.

The left coil outside terminal has the red wire from the Dyna III control unit and the green-blue wire from the main wiring harness attached to it.

 

The right coil outside terminal has the brown Dyan III wire from the control unit attached.

WARNING:
The black wire that goes to the condenser inside the front engine cover is NOT connected to the coils when using the Dyna III electronic ignition. If it is connected, the bike will not start.

The black ground wire from the Dyna III control unit attaches to the right front Allen bolt for the coil bracket. Again, I check that wire for a solid ground using my ohm meter.

I coil the extra wires in two bundles secured with a shrink tubing; one with the leads from the Dyna III control unit and the other with the two leads that go to the points. I zip tie the two bundles together and tuck that into the space between the spine tube and the reinforcing tube.

I install an EME electronic voltage regulator that is not as tall as the original voltage regulator can. There is enough room to mount the Dyna III control unit on top of it. I use Velcro to attach it to the top of the EME regulator. This space gets some air flow from the front so both units should stay cool.

Install Rear Brake Switch

The switch mounts on a tab inside the right rear muffler bracket with two screws. The main wiring harness has a branch with two wires, green-black and green-red, that go the the terminals of the switch. I route this branch under the batter box and secure with a couple of tie wrapes. There is a black rubber cover that fits over the top of the switch to protect the terminals from water and crud.

Install New Oil Pressure Switch

The bike came with a VDO oil pressure gauge and sender. I decided to install the original oil pressure switch instead of the gauge.

The wire for the switch is in the same branch of the main harness that includes the transmission neutral switch.

To prevent potential leaks from the seal between the case and plastic center of the switch, I put some green loctite which wicks into any gaps between them.

The wire terminal was changed to a ring terminal. I remove it and crimp and solder a female spade terminal with some shrink tubing to seal the wire to the spade.

I like to add some flux when I solder even though the solder has rosen flux in the center.

I use two pieces of shrink tubing, a smaller diameter one around the spade and then a larger diameter one around it and the wire.

I install the oil pressure switch into the block with a sealing washer. I don’t over tighten it as that can crack the metal-to-plastic seal and let it leak.

Install Rear Wire Sub-harness

I removed the plug from the rear wiring sub-harness so I can clean the terminals. That allows me to thread the rear harness through holes in the sub-frame starting from the hole in the rear with the plug terminals going in first.

I wrap masking tape around the terminal ends and twist it around the end of a piece of electrical wire I threaded from the front hole and wrap another piece of masking tape around the joint.

When I pull the plug terminals through the front sub-frame hole, I remove the tape so I can put the terminals into the plug.

I use the wiring diagram I made when I removed the terminals from the rear plug and also verify the wire colors match up with the ones in the other half of the plug attached to the main wiring harness.

When I install the rear fender, I attach the rear brake light housing, rear turn signal stalk and turn signals and attach the wires inside the brake light housing.

Main Harness and Sub-harness Routing

I shot a video showing how I route the main wiring harness and the sub-harness’.