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

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:

Final Product

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.

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

Ready To Start – Front and Top Covers Removed

Alternator Stator and Housing Removed as A Unit

Alternator Stator and Housing Removed as A Unit

Alternator Rotor Fits on Tapered Crankshaft Nose

Alternator Rotor Fits on Tapered Crankshaft Nose

Engine Electrics Harness with Labels

Engine Electrics Harness with Labels

Cycle Works Inner Timing Cover Removal Tool

Cycle Works Inner Timing Cover Removal Tool

What's Under the Inner Timing Cover

What’s Under the Inner Timing Cover

Crankshaft Nose Bearing and Sprocket in Cycle Works Removal Tool

Crankshaft Nose Bearing and Sprocket in Cycle Works Removal Tool

Installing Bronze Color Back Plate With Screw Driver Blade

Installing Bronze Color Back Plate With Screw Driver Blade

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

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

Engine Electrics Installed Ready for Front Cover

Engine Electrics Installed Ready for Front Cover

8 thoughts on “1975 BMW R75/6: Replacing Timing Chain, Crankshaft Sprocket & Nose Bearing

  1. Brook, as usual an EXCELLENT write up and documentation!! Thanks to you I feel much more confident about starting on my R100 cam chain replacement.

    • Hi Don,

      Thank you, and thanks for helping me get everything taken apart on this project. I want to come by when you do your project as I also need to do this work on my 1983 R100RS bike, so you can be my guinea pig 🙂

      Best.
      Brook.

  2. I have a 1974 R90/6. I have it down now forpainting the front fender and gas tank…I have had problems with getting the carbs to adjust properly after having them cleaned, (and rodded out) . The only gipe I have with my bike is that the clutch has been VERY stiff and grabby for the past two years. I have not heard from, or about ANYONE having LESS trouble, or problems with ANY bike than I have had with my beemer (only lacks about 800 miles having 300,000 on it) Will get that this spring….I f I stay healthy (82 years of age) I put 3″ straigh-outs on it and it made it TRULY a hot rod bike. Any other KINDS of bikes out there can boast of that many miles?

    • Hi George,

      Thanks for dropping by to read this write-up. You have certainly gotten your money’s worth from the R90/6. I’d like to see the R75/6 roll past 200,000 miles, but that is getting harder to achieve with multiple bikes in the stable.

      Best.
      Brook.

    • Hi Tim,

      Thanks for taking a look. You should have all you need for the R90 project. Check the “Parts and Tools” section where I list all the details on parts. The engine electrical parts are in “Optional Parts”.

      Best.
      Brook.

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