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

Posted on August 24, 2015 by breams

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:

11 BMW R100RS Diagnose Intermittent Low Oil Pressure Light

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.

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

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

Cutting Filter Paper Cylinder From Metal End

Bright Metal Particles

High Pressure By-pass Valve Parts-Mangled and Bent

Fishing Ball Bearing Into Hole

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

Attaching Oil Test Gauge to Instrument Cluster For Test Ride

1983 BMW R100RS Rebuild: Replace Fork Seals, Install Slider Dust Covers

Posted on July 15, 2015 by breams

When I bought the bike, the forks had both rubber fork gaiters and torn rubber fairing boots. But, I can’t turn the forks lock-to-lock as the gaiters interfere with the fairing boots. I think this is dangerous so I’m going to remove the gaiters and the fairing boots and install the black rubber cups on the fork sliders. I will wait for when I do the complete tear down of the bike to replace the fairing boots. I also replace the fork seals since I have to do all the work needed to get to them and I don’t know their condition.

You can read about how I did that work here:

31 BMW R100RS Replace Fork Seals, Install Slider Dust Covers

The fork oil was about the color of the Mississippi river and there was a bunch of it captured by the fork gaiters, so it was well past time to replace the seals and add fresh fork oil.

Fork Seals Leaking Fork Fluid

I decided to leave installation of the fairing boots for when I rebuild the bike. They are very difficult to attach to the fairing holes with the fork tubes installed. I think this will go a lot easier when I have the front fairing panel off the bike and can get clear access to mount the rubber boots.

Old Fairing Fork Boot

New Fairing Fork Boot-I’ll Install it Later

I had a very difficult time removing the fork top nuts. Someone likely used an air impact wrench to put them in. I had to get an 800 Ft-Lb wrench to break them loose. Why do people overly tighten things!!!!!

When It’s Stuck, Get a Bigger Hammer: Impact Driver (800 Ft-Ibs) Needed To Remove Top Bolts

I installed the black rubber dust seal caps with the felt dust wiper on the inside. I learned you have to keep pushing the felt and packing it into the groove until the diagonal cut ends meet. That way it keeps itself tight against the fork tube. And DON’T OIL IT. That just traps grit and dirt in the felt wiper gumming it up.

Fitting Felt Wiper Into Fork Slider Boot

Felt Wiper Installed in Fork Slider Boot

After this work was done, I rode the bike for a couple of shake down rides. It runs pretty well. There are some burned out bulbs in the clock and volt meter and the odometer isn’t working, so I will get those sorted out next. Unfortunately my attempt to fix the odometer only broke it further, so I sent it to Palo Alto Speedometer to repair my clumsy attempt. Sometimes I have to have the pros clean up my mess. Oh well, live and learn.

1983 BMW R100RS Rebuild: Diagnose Charging Problem

Posted on July 14, 2015 by breams

After I got the bike running, I noticed that the volt meter showed low voltage (under 12 volts) when I was riding the bike with the headlight on. Something in the charging system was not working correctly. I read in Bob Fleischer’s material that a failed diode in the diode board would have this symptom and dirty electrical connections and/or alternator brushes that had gotten worn down could also cause low charging current to the battery. He also talked about BMW using rubber diode board mounts at this time. These mounts can break and allow the diode board to fall enough to short against the front engine cover and also contribute to weak or intermittent grounding.

So, I decided to dig into the diode board and test the diodes, replace the rubber diode board mounts and clean up all the electrical contacts. While I am in there, I also cleaned up all the alternator electrical contacts and replaced the alternator brushes. And, I cleaned up the starter relay and voltage regulator contacts. Last, I installed a new Westco AGM battery so I have a known good battery and date of installation.

Here are the write-ups on this work:

I found that all the diodes were good on the diode board. It maybe worth replacing it due to it’s age and as insurance from an unexpected failure, but I’ll hold off on that until I do the full rebuild. Replacing the rubber mounts is not a fun or easy job. I got very frustrated more than once and had to take a couple coffee breaks to get my attitude adjusted. 🙂 But I did get them installed, so with perseverance and patience, it can be done.

After I replaced the alternator brushes and cleaned up all the electrical contacts, I now get 14.5 volts between the battery (+) terminal cable from the diode board and ground with a momentary rise to 15 volts when the voltage relay does it job. I suspect the brushes were the main reason for the low charging current to the battery.

A couple of pictures follow.

Check Diode Board, Replace Rubber Mounts.

Diode Board-Left Alternator Center Tap Wire, Right Battery (+) Wire

Diode Board Back Side Showing Two Connectors

Left Side Diode Board Mount Nuts

Right Side Diode Board Mount Nuts-Note Solenoid Wires Removed & Oil Breather Hose Clamp Moved

Rubber Mounts-One Broken

Location of Large and Small Diodes

Solid Diode Board Mount Kit From Euro Motoelectrics

Alternator with Wiring

Removing Brush Terminal Lugs

Removing (3) Stator Housing Bolts

Alternator Stator Assembly

New Brush (Top) and Shorter Old Brush

New Brushes Soldered To Metal Tabs of Brush Holder

1983 BMW R100RS Rebuild: Diagnose and Replace Failed Neutral Switch

Posted on July 3, 2015 by breams

When I bought the bike in January 2015, the neutral bulb didn’t light and the starter motor wouldn’t work unless I pulled the clutch. I need to figure out what is going wrong in the starter circuit and the neutral switch. I wrote up the work I did here including how I diagnosed that the neutral switch failed and how to replace it:

61 BMW R100RS Diagnose and Repair Neutral Switch

This write-up makes use of some short videos to show what I do. I’m experimenting with how to use video clips to explain things better than just pictures and text can.

There is a longer video at the beginning in which I explain how I use the Haynes wiring diagram and Bob Fleischer’s material to figure out how the neutral and clutch switches work in the starter switch circuit.

I’ve heard fellow Airheads tell me electricity is confusing and a mystery. So I thought maybe showing how I try and figure out how components work from the wiring diagram when I have a problem may be of some value. Here is a direct link to that video.

1983 R100RS Neutral Switch Circuit & Operation

Here are the other short videos I shot that are included in the write-up.

Here are a few pictures from the write-up.

Neutral Light Not Lit

Printed Circuit Contacts for Neutral Switch

Neutral Bulb Pins on Printed Circuit

Neutral Switch with Grunge

Degreased Bottom of Transmission and Engine Oil Pan

Prying Out Center Engine Mount Spacer

Old Switch Ready to Remove

New Neutral Switch and New Washer/Spacer

New Neutral Switch with Plast-Aid Applied to Prevent Leaks

Neutral Light Works 🙂

1983 BMW R100RS Rebuild: Pannier Plastic & Latch Repair

Posted on May 28, 2015 by breams

In 1983, the R100RS came with BMW branded panniers, or saddle bags. Mine have a number of cracks and a broken lid hinge. While I’m waiting for some fork parts to come, I started to repair the panniers. My goal was to try and make the crack repairs invisible. I think I got a B+ this time and learned a lot about how to create the textured surface in the plastic on the outside of the pannier.

I’ve tried a plastic repair product, Plast-aid, before to fix the bulkhead connector on a Windjammer fairing. I’m using it on the panniers. It can be colored using Acrylic paint so the Plast-aid color will match the black panniers. I also fixed a broken latch assembly and learned about locks and keys and how to figure out what key you need for a lock. Here is the link to the write-up on what I did.

46 BMW R100RS Repair Panniers & Plastic

I discovered that two different keys are not enough for all the pannier locks. Some have been replaced so I have four different locks needing four different keys. I posted a note to the Micapeak Airheads forum about this and learned that the latch locks are no longer available, but, Larry Stonestreet, owner of Stoner’s Beemer Stash [[email protected]; 951-813-1704] has the keys I need. So all’s good. There is a nice page on Bob Fleischer’s site about the locks and keys BMW has used with part numbers of the various keys.

Here are some pictures from the write-up.