- Remove Turn Signals, Parking Light, Head Light, Instruments, Ignition
- Remove Electrical Components
- Remove Rear Wiring Sub-harness
- Remove Rear Tail Light and Turn Signals
- Remove Rear Brake Light Switch
- Remove Clutch Switch & Neutral Switch Sub-harness’
- Remove Main Wire Harness
- Various Wire Harness’
Remove Turn Signals, Parking Light, Head Light, Instruments, Ignition
I show how I remove the body panels, front turn signals, parking light, head light, dash, instruments and ignition switch, rear fender, rear tail light and turn signals in this write-up.
- 46 BMW 1977 R100RS Remove, Disassemble Body Work
There were changes made in the wiring to install heated grips and VDO oil pressure and temperature gauges. However, none of these were working: the wiring to the gauges had been cut and the heated grip wiring had been patched and disconnected.
Remove Electrical Components
The bike was updated with dual plug heads and a Dyna III electronic ignition. The stater relay, horn relay and voltage regulator are stock. Removal is straight forward. I took pictures and labeled wire ends to simplify installation.
Remove Voltage Regulator
This is the large rectangular can on the right side of the bike under the gas tank. There is a triangular plug that goes into a socket in the bottom. The wires come from the alternator inside the front cover. I remove the triangular plug and unscrew the Allan head bolts to remove the voltage regulator from its bracket.
Remove Dyan III Coils and Ignition Module
The bike has dual plug heads and uses the Dyna III two port coils (red). The green/blue wire from the main harness plugs into the outer lug of the left coil. The red wire from the Dyna III ignition module plugs into the other spade of the same lug. A second lug toward the inside of the bike has a black jumper wire that plugs into the inside lug of the right coil. These are 6 volt coils, so the black wire puts them in series for the 12 volt ignition system.
The right side coil has a brown wire from the ignition module that plugs in a spade on the outside lug. Note the black ground wire from the ignition module is connected to the right side top engine cover allan head bolt per Dyna instructions.
The ignition module has six wires: a bundle of red, brown and black that go to the coils and ground to the engine and two other wires, red and white, that connect to the hall effect sensor (aka, points) inside the front cover. I remove the module and unplug the two red and white wires from the leads going to the hall effect sensor.
Remove Starter and Horn Relay Sockets and Remove Wires
These are located under the gas tank on the left side opposite the voltage relay.
In front of the relay sockets is a white plastic connector with blue wires. I unplug these.
I unplug the relays from the sockets There is a lot of corrosion on the relay prongs and inside the sockets where the female terminals are located. I plan to replace the relays. I remove the female terminals from the sockets so I can clean them up.
The sockets have a keyed side so they can connect to each other. I slide them apart so I can remove the wires going into the bottom of the sockets easier.
I use a small, thin, flat blade screw driver to compress the tab on the side of the female terminals inside the socket so I can remove them. As shown here, the slot is the small rectangular hole centered next to the longer slot the female terminal fits into.
I find pushing the screw driver into the slot and twisting it a bit while pulling on the wire makes it pretty easy to remove the terminals from the socket.
As I remove the wires from the sockets, I make a diagram showing the location and color of each wire so it will be easier to connect them again. This is my short-hand for the colors:
Some of the wires I labeled as “Brown” (BR) are actually red. The insulation had discolored. I figured this out when I put the cleaned wires back into the sockets. See the write-up about installing the wiring and electrical components where I have a video showing how to use the wiring diagram and the terminal numbers on the sockets to ensure the correct wire goes into the correct hole in the socket.
The starter relay has wires from the main wiring harness, the (+) battery cable and from the alternator inside the front engine cover via the front slot of the inner cover. The horn relay has a jumper from the starter relay socket, a ground wire, a black wire going to the horns and a wire coming from the main harness that goes to the horn button.
Remove Rear Wiring Sub-harness
The wiring to the brake light and turn signals goes through a separate sub-harness that plugs into the main harness near the left side of the battery box.
The sub-harness routes inside the rear sub-frame via a hole near the left handhold and a second hole at the back of the sub-frame in the middle.
Remove Rear Tail Light and Turn Signals
This shows how I removed the rear tail light assembly and the turn signals from the rear wire harness.
- 46 BMW 1977 R100RS Remove, Disassemble Body Work
With the wires disconnected from the tail light and turn signals, the rear sub-harness can be pulled through the sub-frame to remove it. Since I am going to clean the terminals on the rear sub-harness, I remove the male pins from the rear sub-harness and pull it out the rear hole using the round male terminal pin removal tool. I make a sketch of the pin locations in the plug before removing them.
Here is the rear sub-harness with tail light attached with the rear sub-frame removed.
Remove Rear Brake Light Switch
There are two wires that go to the rear brake light switch. I remove the rubber cover, then the two screws securing the switch and remove the two wires.
Remove Clutch Switch & Neutral Switch Sub-harness’
The clutch lever has switch and a small sub-harness that attaches to a plug in the main harness near the left side of the steering head. There is also a short sub-harness that connects to the neutral and oil pressure switches. This plugs into the main harness near the left front foot peg. I unplug these sub-harness’.
Remove Main Wire Harness
With all the electrical components and sub-harness’ disconnected from it, I remove the main wire harness. I snip the zip ties securing it to the frame with wire cutters. As I pull it forward, I label the branches and ends of wires with the component they connect to so it will be simple to reinstall it. When the main harness hangs down beneath the headlight bucket, I remove the headlight bucket with the main wiring harness and handle bar switch wire harness’ attached.
Various Wire Harness’
Here is a summary of the various wire harness’ I removed.
Main Wire Harness
Here is a photo of the main harness showing what the branches connect to.
Fairing and Instrument Panel Sub-harness
Here is the fairing and instrument panel sub-harness. The ignition switch wires are part of the main harness.
Heated Grips Sub-harness
This is the heated grips on-off switch and sub-harness.
And the rear sub-harness with the tail light and turn signals still attached to it is shown below. Note that I removed the plug that goes on the end of this harness so I can clean the pins.
Rear Sub-harness Plug Pin Diagram
one comment as i glance thru this brook is
i always make reference to which end of the ‘plug’ i’m looking @ :
male /female back side / front side
or plug in side / wire side … as i write down wire color and location because it could be depending on the plug type) opposite from the wrong end. especially when shooting trouble.
cause @ least for me 6 hrs, 16 days or 6 months later i’ll need that info again and it may not appear to be clear to me … … then.
Wow ! was that R100 still running or sitting with all that corrosion.? I think you are just the Man I need to ask a question . I am a Machinist who is challenged in electrical areas. On occasion I do not get a green neutral light when I am in neutral (not false neutral) No doubt I need to change the neut. switch which I can do (sometime) . Meanwhile I would like to know how to bypass the system and get going when this happens. I realize I will not have starter protection in the event I hit the wrong button when riding. Hope you can help, thanks Henry 1980 R80/7 also 1967 R50/2
Amazing that it was running before I started the rebuild.
I’m afraid I don’t have any advice on how to bypass the neutral switch. That said, sometimes the pins in the large rubber connection to the back of the instrument cluster get dirty and a cleaning fixes flaky lights. Also, the internal flexible circuit board is prone to having copper tabs fracture where they bend into the hole for the light bulb sockets.
You may want to look at these potential problems if you haven’t already.
This write-up shows a repair I made to the instrument circuit board.
62 BMW 1983 R100RS Repair Instrument Circuit Board Foil
I hope this helps.
Great stuff Brook! Thank you as always. May your site ever roam cyberspace!
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Hi Brook – Do you happen to have a photo of where the heated grips sub harness connects to the main harness on the 1977 R100RS?
I thought the heated grips plug into the front brake light switch for power, but on this main harness, the front brake switch goes into main harness without a connector in the middle.
On your Youtube Channel, the 1983 100RS shows the front brake light switch has a short pigtail, which would also the use of this pigtail (part number 61121243981)
I’m trying to add heated grips to my 1978 R80 /7, so looking to see where the sub harness goes. Can I power from the clutch level switch?
On my 1977 RS which came to me with heated grips, the wiring and fuse that power the grips was connected directly to the battery. The BMW switch for turning the circuit on was mounted on the right headlight mounting bolt.
If I’m not mistaken, my heated grips were not installed at the factory.
Bob Fleischer (aka Snowbum) has several wiring diagrams on his site for heated grips in this document.
I hope that helps.
Thanks for the clarification Brook. Yup, I’ve reviewed Snowbum’s site a few times, but I’ve never been very good at reading schematics 🙂 I usually do better when viewing pictures or videos.
Interesting that your bike’s previous owner wired it directly to the battery. I might go that route too, but would rather go off the ignition switch to make sure I don’t accidentally leave it on.
Yes, having the ignition turn off the heated grips is the better way to go.
I’d look inside the headlight shell for any empty GREEN/black terminal on the connector block. If there is one, that would be a sanitary way to get power.
If you put a fuse in the heated grip wiring, you could also look for any empty GREEN terminals on the connector block. I’d start with a 3 amp fuse for the heated grips. If it blows, go up to an 8 amp fuse.
If no spare terminals on the connector block inside the headlight shell, you could get power off the coil where the GREEN/Blue wire goes to bottom terminal on the left side coil. There is usually a spare spade terminal there. The coil power is controlled by the ignition switch. But, the GREEN/Blue wire is not fused, so again, I’d add a fuse block to the wiring.
I hope that helps.
I found the picture of my heated grips wiring harness (part# 61 12 1 243 981 NLA) when I removed it.
It looks like they connected it inside the headlight shell. There is a connector with GREEN/Black wires and a “Y” off the female spade terminal (next to the BROWN ground wire in the picture). On my bike someone plugged in a GREEN wire with ring terminal to connect to the battery (+) terminal.
It looks like the idea was to remove one of the GREEN/Black wires on the connector block, plug in the heated grip female terminal with the “Y” (the clear terminal with two GREEN/Black wires) and then connect the existing GREEN/Black wire you removed to the other leg of the “Y” (the white plug with a male terminal). That way the grips are fused and you can add heated grips even when there are no spare GREEN/Black terminals on the connector block.
The white terminal strip with screw terminals at the lower right was where the four wires from the grips plugged into. Each grip had it’s own BROWN ground wire so both of them went to the single BROWN screw terminal and the two other grip wires went to the GREEN/Red terminal.
The “T” shaped white connector on the lower left plugged into a wire (part# 61 12 1 243 980) that went to the BMW switch (part# 61 31 1 243 007).
I hope that helps.
Thank you Brook, that is super, super helpful. There are a couple of places that are remaking the NLA wiring harness, so that’s what prompted me to take up this project again. It’s now possible to order all of the necessary parts to get an OEM (or OEM looking) setup.
You’re welcome. Can you post who is making the replacement wiring for the heated grips? It would be helpful.
Here are the two that I remember, but I have to correct myself, I think these are reproductions of the OEM wiring harness for the later bikes:
I think I have another source that I bookmarked, so when I find it I send you that link too.
So this harness has a connector that would plug into (or jumper) the front brake light switch pigtail on your 1983 bike. Still if I change out the connectors for regular spade connectors, I could plug them into the fuse block as you suggested.
Dear Brook, I want to thank you for what you do. My bike, 100RS/82 almost catched fire due to old worn wiring. With the help of your detailed guidance I was able to replace the whole wiring harness, check and double check, and see your instructions again and again and today I managed to start her up. Everything worked perfectly.
I also overhauled master cylinders, calipers, front fork (aligned), steering bearings, carburators and some other. You made me feel so confident and assured, and finally proud. Thank you again, I have learned so much!
Cool beans. I’m pleased my documentation was helpful to you and another airhead is back on the road 🙂