1977 BMW R100RS Transmission Work

It has taken some time, but I finally finished writing up the work I did on the transmission, and you can find it here.

I included several short videos that show how the transmission gears and the shift cam assembly work, and several that cover other details of the work.

Here is a play list of all the YouTube transmission videos I made.

This is the most critical, precise piece of work I’ve taken on. Before doing this project, I did a lot of research. I had access to special tools, a shop press and advice from two local airhead mechanics. Without those resources, and spending a couple months trying to learn what I needed to know about this work, I wouldn’t have attempted to do it.

Despite all that, I managed to overlook a new, but wrong size, $2.95 circlip that holds the cam roller on it’s pin. It separated company from the pin about 2000 miles after I finished rebuilding the bike. I was in Indiana at the time on my way to the 40th RS rally in Pennsylvania. Mr. Cutter, who was attending the rally, stepped in and devoted a Sunday to save my bacon. Watching him do the work in a day I had labored over for weeks reinforced the value you get from someone who has spent 45 years making mistakes and learning from them so you don’t have to 🙂

So, in retrospect, I should say I relied on three airhead mechanics to do this work 😉

4 thoughts on “1977 BMW R100RS Transmission Work

  1. Hey Brook,
    Thank you for all the great information found on your website. Gonzo is a beautiful bike! Currently I am studying how to rebuild and repair the transmission. It does not seem like a task beyond ability and am trying to acquire the proper tools to open the gear box and take apart the contents for examination. Cycle Works is shipping me the flange puller and measuring plate this week. Once the gear box is opened, some if not all the bearing must be pulled. I looked at the bearing puller you show, and it is from Harbor Freight. Will you please suggest the HF item number to me as which of the two HF bearing puller items I should buy to remove the bearings?

    The bearings bring another question to mind. I have taken axel bearings out of a car, removed all traces of grease and repacked the bearings for reuse. Do we have to throw away the old bearings in the transmission, or can they be cleaned, repacked, press fit and used again if they are not notchy? A bearing set from Bob’s BMW is about $190 plus shipping. This has been a twelve-year Airhead odyssey for me so far and I try to do all the work if possible. My R100 RS five-speed transmission, built in May of 1976, was rebuilt by Ted Porter out in California about 15K miles ago. That was before I knew about Tom Cutter right here in Pennsylvania. What Tom Cutter believes has happened is a broken 519 gear wheel on the input drive shaft, but I will not know for sure until it is taken apart for inspection. You had Cycle Works chrome a section of your shaft. What advantage was gained from that detail? The magnetic drain plug has never shown much of anything, certainly not metal parts. Again, Thank You for your time and efforts helping us other Airheads stay on the road.

    In summary; What HF item number do I need? Can the bearings be reused? And, Why the Chrome hardening and what did that cost? Thank you for your time and attention, with any luck and lots of planning like you did, a three-dollar Circlip won’t spoil my day.

    Best Regards,

    PS Had to leave a Post Comment with questions as I do not have a direct email address, sorry about that.

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