The Glorious BMW R90S Restoration Project:

 The Project:

The R90S:

The project bike is a 1975 BMW R90S.

    The R90S uses a BMW type 247 horizontally opposed, air-cooled, twin cylinder engine with a displacement of 898cc. This configuration is popularly known as a "Boxer". For those who are really into it, it's also called an "Airhead".  This version of the Boxer engine produced 67 BHP, and propelled the smiling rider to reported speeds of over 120 MPH.

    The R90S was among the first "Superbikes" to be produced, and set the standards by which performance motorcycles were judged. A cafe-style "Bikini" fairing gave it a sleek, distinctive look that is, for better or for worse, very period.  You won't mistake an R90S for anything made in the 90's, I guarantee it.

    Between 1973 and 1976, 17, 455 units were produced, before the model was replaced by a slightly larger displacement version, the R100S.

    Here's an example of what the bike is supposed to look like:

My R90S:

    My R90S was brought to my house on New Year's Eve Day, 1998.  The previous owner and an associate purchased the bike at Auction some time previous.  The bike had been wrecked in what appeared to be a head-on collision with an object of some mass, which proved to be reluctant to move.  Significant damage was done to the fork tubes, which were bent, the frame, which was bent under at the headstock, and the fairing, which was missing and is presumed destroyed.  Although other minor damage was evident, the bike appears to have been under good care, and was in very good shape at the time of impact.


1/1/99: Bike arrives.
10/7/99 Some leads on needed parts.
11/16/99 Frame and Fairing arrive.
11/21/99 Frame is prepped.
12/1/99 Swapping begins
3/8/00 Coming into focus.


           Images of how the bike looked this day: r90s2t.jpgr90s3t.jpg
Assessment of the damage: I spent some time looking over what was usable, and what has to go.  There are two lists:

Things that are okay:

  • The engine, which turns, appears to be in relatively good tune (valves look good)
  • The wheels.  Surprisingly, there appear to be no loose spokes, and the front rim seems okay.  Tires are low-mileage and in great shape.
  • Seat and tank.  Seat is in nearly perfect condition. Tank has been repainted, and evidence of  a large corroded spot is visible.  Also, some impact damage is apparent, probably from the final collision.
  • Transmission appears to shift well and positively, although further inspection is obviously required.
  • Electrics seem to be okay.  Suprisingly, the battery was still holding a charge, and everything that was still attached (turn indicators, brake lights, headlight) all seem to function normally.
And, things that need to be replaced:
  • Frame.  This is obvious.  Someone has tried to straighten the frame already.  Experts seem to agree that you get one chance, and this one missed.  I'm going to go ahead and just figure on replacing the thing.  It may lose some collector value, but I'm not doing this as a finanacial investment, I'm doing this to finish a project and have a nice bike.
  • Fork tubes.  Fortunately, the previous owner was able to find another set, and these were included with the bike.  Just a matter of getting them in.
  • Exhaust.  The /6 exhaust was not part of the deal, and will be returned to the previous owner for inclusion on some other project.  Great shape, though!
  • Shocks. The original shocks were removed for the same purpose as the exhaust.  I'll probably upgrade these to Konis, just 'cause.
  • Fairing.  Ain't one here, and I want one.  I'd prefer to get a nice used one, since a new one will probably cost me as much as the bike itself.  And that's before it's painted! Careful examination eventually revealed traces of some of the fairing's mounting hardware, which supports my destruction hypothesis.
  • Mirrors.  Ain't there, gotta have 'em.
I wanted to get some pictures before doing any major work, but the tank and seat looked so nasty that I couldn't resist polishing them up.  The shots you see are just as the bike arrived, except for this.

I'm currently following some leads on the internet, priority is getting a frame.  The plan is to move everything over to the new frame, part by part, cleaning and servicing as I go, rebuilding as necessary.


After many months of being distracted from the project (new job, other projects, the usual), I have finally been able to locate a usable frame and fairing, discovered on the IBMWR BMW motorcycle marketplace.  The check is going out tomorrow.

Once the frame arrives, priority will go to establishing a workable skeleton upon which to hang the parts as they are removed from the old frame.  This involves:

  • Installing new steering head bearings
  • Rebuilding the forks
  • Moving the rear sub-frame over
  • Moving the drivetrain
At this point, there will be enough structure on the new bike to get it standing on its own two wheels. (with a new centerstand, of course)


The frame and fairing have arrived.  The fairing is in need of paint and mounting hardware, but the screen is in fantastic shape.

The frame is from a 1977 R100S.  It arrived in a very interesting manner, and is need of some minor surface rust elimination.  So far, it looks straight, and none of the rust is structural, or in any critical area.  Overall, I am very pleased with the purchase, and will highly recommend Mr. Lawrence Hogarth. Lawrence is a very knowledgeable guy, and a very straight shooter. I'd do business with him any time!

Since the fairing will defnitely require painting, and the tank could use  new paint and some very minor bodywork, I am thinking about what sort of paint job to put on the bike.

A couple of ideas:

  1. I am thinking of my Specialized Epic bicycle, which has a beautiful finish, with tons of depth.  It fades from a red at the ends of the tubes into a natural carbon fiber near the centers.  Obviously, the BMW wouldn't have any carbon fiber, but a hint of red around the headlight, fading into a deep black might be kinda cool.
  2. Of course, trying to duplicate an original Silver Smoke scheme would be authentic, but the growing number of non-original items on the bike is starting to make me think that an orignal scheme at this point would be somehow inappropriate.  And I'm not actually that much of a fan of the Daytona Orange scheme...
In any case, at the moment, I am thinking it will be something with a lot of depth.  Of course, ask me again after polishing out coat #20!


The new frame has been prepped, and swapping will begin presently. The prepping process mainly involved spot treatment of a couple suspicious looking spots that looked like they were starting to get interested in rusting. These were shot with a rust arrestor, primed, and then painted. All threads were cleaned and inspected, and all fasteners checked.


Figiring I'd start from the front, I went ahead and removed the fork stanchion tubes that had been pressed into the triple clamp. This freed up the steering head, so I went ahead and moved that over to the new frame. Surprisingly enough, the steering tube and the triple clamp showed no malformation under inspection. This was a little surprising, given the nature of the accident. I am not complaining, however, and the frame started to look like it might someday be a motorcycle.
The damping rods in the forks also proved to be straight, and showed no signs of damage or lack of proper function.
At this time, unfortunately, the pressures of the end of the year took their toll on my time and money available to work on this project, so there was a small hiatus...


After a few months of inactivity, I finally got some time, energy, and a little money from a tax refund, and dove back into the project.I decided that it was time that the project stopped looking like a broken motorcycle sitting next to a few strange-looking hunks of metal. So I moved over the rear sub-frame, the ignition coils, and the battery tray. This had the twin result of making the project actually look like some progress had been made (very important psychologically), and also allowed some more strategy to be devised for attacking the rest of the project. I am still waiting for some small parts to arrive for the forks, which will be installed ASAP. The next subject to tackle is to move the swingarm, final drive, and rear wheel over to the new frame. It has also become very apparent that the wiring harness for this bike is going to represent some serious strategy. There are wires going everywhere, and clearly the way the harness wants to be removed is by loosening everything up, and then being pulled by the headlight out of the front of the frame. If you're trying this, make sure to use lots of masking tape, and label every little connection.
In attempting to remove the swingarm, there are some other words of warning: the aperture in which the pivot pin and its locknut reside is too small to admit a standard 27mm socket (a hard one to find on its own). Plan to either use a bench grinder or a lathe to turn down the outside diameter. Owning neither, I discovered that it is very difficult to find a machine shop willing to do any turning at 4:00 in the afternoon.
Many thanks are due to the good folks at BMW/Triumph of Santa Cruz, for their help and expertise on this project, as well as keeping the rest of my stable running well.

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This page copyright 1999, by Michael Zenner.  BMW, R90S, and the BMW roundel are trademarks of BMW. Last updated November21, 1999