1983 BMW R100RS Remove Rear Fender Assembly

I’m making progress on getting to where I can remove the electrical system. I finished taking off, and taking apart, the rear fender assembly that includes the license plate bracket with side reflectors, tail light housing, turn signals and stalk, the cowling tool box and the rear wiring sub-harness.

You can see what I found and how I did the work here.

Rear Tail Light, & Turn Signal Assembly, License Plate Bracket & Rubber Mud Flap

Rear Tail Light, & Turn Signal Assembly, License Plate Bracket & Rubber Mud Flap

Tail Light Reflector Wiring Detail

Tail Light Reflector Wiring Detail

Rear Wiring Sub-Harness Plug Location

Rear Wiring Sub-Harness Plug Location

Rear Fender Assembly Removed

Rear Fender Assembly Removed

1983 BMW R100RS Remove Tank, Seat & Fairing

Due to the blizzard in Denver yesterday, I had time to finish up some documentation on the project so far and post it to my site. The focus has been on the fairing disassembly and a catalog of the fairing mounting hardware and where it goes. I found existing parts fiche aren’t very helpful about what fasteners go where.

Here is a link to two new publications.

52 BMW 1983 R100RS Remove Seat and Seat Cowling
46 BMW 1983 R100RS Remove Fairing, Dash, Volt Meter, Clock, Ignition Switch

I included a couple videos, one of which shows details of how all the fairing panels are connected.

Here is how the bike looks now.

Tank, Seat, Fairing & Brackets Removed

Tank, Seat, Fairing & Brackets Removed

And the stack of bins the parts are going in, which will increase as I get down to the frame.

Bins for Disassembled Bike Parts

Bins for Disassembled Bike Parts

1983 BMW R100RS Project Restart; A New Direction

I bought a 1983 R100RS in January 2015 just before I retired so I would have a project to work on. At that time, this was to be the RS I always wanted. I fell in love with the RS the first time I saw one in 1977, so what better way to kickoff my new retired life than to own one and restore it.

In 2015, I corrected several problems and did some needed work:

  • Fixed a flickering oil pressure light
  • Fixed a flickering charge indicator light
  • Rebuilt and refinished the carburetors
  • Replaced the alternator brushes
  • Replaced the broken rubber diode board mounts with metal ones along with the diode board
  • Fixed all the cracks in the panniers and welded the broken pannier frame weld.

After that work, I rode the bike for a few months and several hundred miles and had every intent of finishing the rebuild when winter came. But, I got side tracked with some needed refresh work on my 1975 R75/6. And then in early 2016, someone put a first year, 1977 R100RS up for sale. Long story short, I bought it. And then I decided to restore it so I could ride it to the 40th R100RS anniversary rally in Pennsylvania in September, 2017.  I posted a couple blogs about that ride and was asked to publish three articles about the build and the ride in the BMW MOA magazine. Of course, I published a lot of documentation about that build here:

So, it’s now March 1, 2019 and I’m ready to restart the build of the 1983 RS. But, I changed direction from restoring it to doing a resto-mod and converting it into an RT. I refer to this as the R100RS/T build project.

I revised my original build plan to reflect the new end-state and I added a video walk-around of the beginning condition of the bike. It’s a whole lot cleaner than when I brought it home in 2015.

I plan to make a number of modifications to improve performance, handling and appearance beyond the conversion from an RS to an RT, I summarized what my plan is in the updated build plan you can find here:

As on all my projects, I’ll continue to add links to how I did various parts of the project to this project build index:

So, stay tuned.

1983 R100RS Repair Instrument Circuit Board Foil

One indicator bulb in the instrument housing was not lighting. I pulled the instrument cluster out and tested the bulb which was good. However the foil trace that goes on the tab inside the hole in the circuit board the bulb holder plugs into had broken.

Tab Bulb Connector Lead Touches-Copper Foil Missing

The Tab The Bulb Holder Lead Touches-Copper Foil Is Missing

I used some copper foil to make a repair and I documented how I did it here.

The same technique can be used to repair any of these boards when a cracked or broken foil trace causes intermittent or complete bulb failure bulb. But sometimes the circuit board is broken, badly corroded and it isn’t salvageable.

BMW no longer sells the circuit board but you can find used ones for sale on eBay and some are in good condition. However someone took the time and effort to design a replacement light housing and circuit board that uses LED lights instead of the original incandescent bulbs. For a badly damaged circuit board where the simple fix I made is insufficient, these replacement boards will likely do the trick. I’ve not had occasion to install one of these, but you will find information about them here:

1983 R100RS Rebuild: Oh S^%$t The Oil Light Came On!

Since I got this bike running a month ago, I’ve been taking short trips with it so I can have some confidence it is reliable. I was riding along at about 50-60 MPH on a 93 F day when all of a sudden, the red oil pressure warning light came on just as I turned on to the road to my house. I immediately hit the kill switch, pulled the clutch and pulled over to the side of the road. I waited for a minute and then started the bike again. The oil pressure light went out immediately. Hmm.  I started riding and about two minutes later, the warning light came on again.  So, I went through the same drill of immediately stopping the engine and waiting for a bit. On start up, the oil light went out immediately.  This time I made it home just as the light came back on.  Not a good sign.

So, I’ve been on a journey to isolate why the low oil pressure light comes on intermittently. I found several problems in the oil system of this bike and corrected them. You can read about what I did here:

I took apart the oil filter and inspected the paper, but the consensus of folks on the Micapeak Airhead forum was there wasn’t anything to worry about in the filter.  Big sigh of relief.

As I continued my investigation I diagnosed and fixed a couple problems in the engine oil system. But I’m not absolutely certain I have found the problem causing the low oil pressure light to come on. I’ve ruled out failures in the engine oil system and am convinced the oil pump is working properly, the engine oil passages are not blocked, the oil seals are not leaking, the oil pickup and screen are okay and the oil level is correct.

The electrical circuit is now the most likely reason for the intermittent low oil pressure light coming on. The last thing I replaced is the oil pressure sender switch even though when I originally tested it, it worked. But, it’s the next most likely component to have a problem due to its mechanical action. Here’s a short video of the insides of that switch.

Inside Oil Pressure Sender

I’m hoping the next hundred miles or so I don’t see that oil light on the dash anymore, but time will tell.

Here are a couple pictures from the detailed write-up.

Distance to Measure From Edge of Filter Can to Top of Engine Block

Distance to Measure From Edge of Filter Can to Top of Engine Block

Vernier Caliper Reading 3.82 mm Canister Depth

Vernier Caliper Reading 3.82 mm Canister Depth-Much More than 3 mm Specification

Cutting Filter Paper Cylinder From Metal End

Cutting Filter Paper Cylinder From Metal End

Bright Metal Particles

Bright Metal Particles

High Pressure By-pass Valve Parts-Mangled and Bent

High Pressure By-pass Valve Parts-Mangled and Bent

Fishing Ball Bearing Into Hole

Fishing Ball Bearing Into Hole

White ($2,000 O-ring) Installed in Filter Cover

White ($2,000 O-ring) Installed in Filter Cover

Attaching Oil Test Gauge to Instrument Cluster For Test Ride

Attaching Oil Test Gauge to Instrument Cluster For Test Ride