1975 BMW R75/6: Replace Rear Main Seal, Oil Pump Cover, O-ring, Refurbish Clutch

Posted on February 21, 2016 by Brook Reams

I have completed documenting this work for those interested in the parts, tools and procedure used. You can find my write-ups here.

I did the same work on my R75/5 as well which you will find on my site. The main differences between these projects were using Southland Clutch to refurbish the R75/6 clutch where I replaced the clutch on the R75/5 project, and not damaging the rear crankshaft thrust washer this time. 🙂

This is the first time I used Southland Clutch. I am very pleased with their knowledge of airhead clutches, their courteous and prompt service and the quick turn around at a price about one-half the cost of the new parts. I am adding them to my Resources list.

Engine Out of Frame Showing Clutch Compression Ring

Small Bolt in Alternator Nose Keeps Crank From Moving Forward

Small Bolt in Alternator Nose to Keep Crank From Moving Forward

Hardened Clutch Install/Removal Bolts, Nuts, Washers

Removing Every Other Clutch Bolt with Battery Powered Impact Driver

Friction Disk Uneven Wear: Note Part Number Still Showing on Side Facing Pressure Plate

Cycle Works Flywheel Puller Parts

Old Style Oil Pump Cover with Phillips Head Screws

Evidence of Oil Leaking Past Rear Main Seal

Groove Cut in Flywheel by Old Style Seal

Cycle Works Rear Main Seal Puller Parts

Heating New PTFE Seal in 150 F Engine Oil to Soften

Forming Crank Rear Oil Seal on Flywheel Ring

Tightening Flywheel Bolts on Cycle Works Seal Installation Tool

Flywheel Installed

Southland Clutch Refurbished Clutch Compression Plate

Southland Clutch Refurbished Clutch Plate

Southland Clutch Refurbished Pressure Plate

3 Clutch Bolts Added with Long Installation Bolts

Transmission Ears Aligned With Clutch Housing

Refurbished Clutch Installed

1975 BMW R75/6: Replacing Timing Chain, Crankshaft Sprocket & Nose Bearing

Posted on January 13, 2016 by Brook Reams

This bike, a 1975 R75/6, is the first BMW I bought and now has almost 106,000 miles on it. It is the first bike I rode more than 1,000 miles in one day back in 1976 and is the first build project I completed in 2010 and documented here:

1975 R75/6 Rebuild Page

Final Product of 2010 Restoration Project

I have several projects that I didn’t get to during the build. One of these is replacing the timing chain which I document here with a lot of pictures and detailed step-by-step procedure.

11 BMW R75/6 Replace Timing Chain, Crankshaft Sprocket, Nose Bearing

My bike has the duplex, dual row chain, while starting with the /7 series, the timing chain is a single row chain. This procedure should help you replace a /5, /6 or /7 series timing chain, but some of the parts will be different as I note later.

Since I stripped the bike I have the engine out of the frame, but most people will do this work with the engine in the frame. Although it is an option to remove the front wheel and forks to have clear access to the front of the engine, I think the work can be done without removing them.

Before starting this project, I reviewed material available on the Airheads Beemer Club site, www.airheads.org: I believe you can access the links below even if you are not a member, but consider joining this group if you want to contribute to the Airhead culture. I read material on Bob Fleischer’s blog site, and I posted a number of questions to the Micapeak Airheads forum whose members are legend for providing thoughtful advice and encouragement. You should add these resources to your toolkit as they are authoritative with valuable information.

In particular, I want to acknowledge Ron Cichowski, Tom Cutter, Bob Fleischer, Doran Shields, Marten Walkker and Eric Zwicky on the Micapeak Airheads forum for answering my questions. Also, a local Colorado Airhead, Don Wreyford, came by to kibitz and help with the disassembly process. Don has always been generous with his time and knowledge. And, my youngest son, Branden, shown in many of the photos with the electric yellow shirt, helped me on the entire project with wrenching, picture taking, and good ideas and advice when we needed to stop and reconsider what we should do next. He is turning into an accomplished Airhead wrench and lover of Bavarian iron.

Here are a couple pictures from the detailed writeup.

Ready To Start – Front and Top Covers Removed

Alternator Stator and Housing Removed as A Unit

Alternator Rotor Fits on Tapered Crankshaft Nose

Engine Electrics Harness with Labels

Cycle Works Inner Timing Cover Removal Tool

What’s Under the Inner Timing Cover

Crankshaft Nose Bearing and Sprocket in Cycle Works Removal Tool

Installing Bronze Color Back Plate With Screw Driver Blade

Verifying Crankshaft and Camshaft Sprocket Orientation (White Marks) After Installiing Timing Chain

Engine Electrics Installed Ready for Front Cover

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

Posted on August 24, 2015 by Brook Reams

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 Brook Reams

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 Brook Reams

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.