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post-bmw1.jpgWe’ve received a number of email requests from readers asking for more project coverage in general and for more automotive project coverage specifically.  Well, ask and you shall receive.  This first Toolmonger “project garage” post will cover the beginning stages of one of the automotive projects we’re currently undertaking: the teardown and rebuild of a wrecked BMW “airhead.”

BMW fans refer to their line of horizontally-opposed-air-cooled-twin series of bikes as “airheads.”  We came across this particular example — a 1976 R90/6 — as a “haul-it-off” special in the Fort Worth area.  As best we can determine it was parked in “as wrecked” condition after an accident about five years ago.  Apparently it was “t-boned” at low speed from the rider’s right.  Though there’s certain to be some frame damage, the bike rolled straight and appeared surprisingly together considering what it’d been through.

Read on after the jump to see what we found when we got it back to shop and tore into it.

First Inspection

Though it does look quite good considering the accident, there’s no doubt that this bike has been seriously damaged.  Worst of all, after sitting for years, the gas in the tank had separated, rendering it one of the stinkiest bikes we’ve come across. 

post-bmw2.jpgThe previous owner had added a ton of aftermarket items including a large Windjammer fairing, a large trunk boot, and a trailer hitch.  The wiring on the hitch was nasty, chopped into the factory wiring harness in numerous locations.  The hitch was bent, though we probably would have discarded it anyway.

Truth be told, we think turning the relatively sleek R90/6 — which is essentially the little brother of the R90S of racing fame — into a German Goldwing is heresy, so as we began tearing the bike down we placed it into four “piles:” the bike itself, large items we intend to keep (in storage during the rebuild), small items we intend to keep (in the shop during the rebuild), and items destined for the dumpster.

Starting the Teardown 

Removing the busted fairing was easy, as was removing the trunk boot.  Once they were gone you could immediately begin to see the lines that made these bikes so popular in the late 70s.  We imagine that when we finally get this bike together we’ll opt for the slick bikini fairing.

The tank came off with a few bolts and some pulled fuel lines, and after numerous breaks for air we managed to clean out the spoiled fuel.  Even though the tank’s pretty heavily damaged and certainly not intended for re-use, we did triple-bag it (just in case of the smell) and put it in the “storage” pile in case we need to reference it in the future.

post-bmw3.jpgNext came removing the seat, which appears to be a larger “touring” seat released by BMW as an option after the R90’s manufacture.  We’re not sure if we’ll re-use the touring seat or replace it with the sleeker racing-style seat, but we saved it anyway as it’s in pretty good shape.  When removing the seat we found the under-seat storage compartment filled with some tools that we know’ll come in handy later: the factory BMW toolkit as well as a number of “modified” hand tools, such as a large socket lathed down to fit in tight spots. 

The wiring harness for the R90/6 is located inside the headlight housing, which in this case is covered with a rubber plug because of the Windjammer installation.  After removing the rubber we were able to carefully remove the entirety of the wiring harness — such that it is, considering the clunky addition of the trailer wiring kit — and store it for repair later. 




And here we have it — the basic R90/6 ready for work.  In our next installment we’ll walk through the separation of the rear-wheel and forks, and hopefully soon after that we’ll fabricate a nice engine stand to hold the engine while we tear it down.  We’re also beginning research into who can help us straighten the BMW’s frame and forks.  Of course we’ll let you know how it’s going.

Check back soon for updates on this and a number of other projects we’ll be bringing into the garage over the next few weeks.  And if you have any specific suggestions for projects, don’t hesitate to drop us a line or leave a comment.  We’d like to know what, specifically, you’d like to see more of.


15 Responses to Project Garage: BMW Airhead Part 1

  1. Eugene Halligan says:

    Very interesting project.

    I’m a wannabe bike spanner jockey and will follow your project with interest.

    Trying to decide on an old BMW airhead (75-100) or an old Guzzi (T-750, Le-Mans or some ‘Tonti’) as a worthy project to learn on and have as a second bike for scrathing around on.

    Your thoughts?

  2. Paul says:

    I’d go with the BMW. There were a lot more of them made and more currently in running condition. Used parts are easier to find and new parts are still available to some degree.

    The BMW is going to be more expensive, but if you break down in Montana you’ll have some hope of finding parts. For the Guzzi I doubt you will find any dealer support at all. There are 5 BMW dealers in my area and 2 Guzzi dealers, and this is in the SF bay area.

    Plus, there are a lot more after market acessories available for the BMW. And more folks who know something about fixing them.

    I live on one of the most popular motorcycleing roads in the Bay Area (Highway 9) and the ratio of old BMW’s to Guzzis is about 25 to 1

    Paul Schwartz
    74 R90S (black and silver)

  3. Brad Belk says:

    I am at about the same point in the same project on a 1975 R90 and I am very interested in the outcome of your project. I drove it home and while it was running, it was very rough. Its just in specs for compression. I have a couple thousand in parts coming and I have not gone into the motor yet. My rough plan is to replace the exhaust system, cables, shocks, switches, fork seals and get it running. Once its running, I will make decisions on the engine work.

    Here is my question. How quickly will the transmission splines tear up if they need grease.

    I was thinking of putting that check off until later.


  4. Josh says:


    It depends.

    I was surprised how easily the transmission is to remove from these bikes. he ‘Boxerworks’ forum is a great place to get questions like this answered.


    It is a friendly place, just don’t ask which oil to use. I have been through some interesting repairs with their help.


  5. MIKE says:

    don’t even screw around trying to repair the wiring harness. OEM replacements are readily available and inexpensive. Check out Blue Moon Cycle, Bob’s BMW, and Eurotech online catalogs. You can then shop around for best pricing.

    One of the advantages of working on the Beemer is BMW’s continued support for their older models and the availability of new parts rather than NOS, salvage, or plain unobtanium.

    Don’t be too hasty in pitching the gas tank. Check out the POR15 product line for restoration products.

    You will find that airhead repair is probably the most thoroughly documented motorcycle resource on the web.

    frostbite falls, MN

  6. MikeR says:

    Cool bike, any updates on this project?

  7. Dominic says:

    You’ve picked a good project. All you and the other posters intend to do is correct, and yes the BMs are the most covered marque on the web – am doing an R65 mono at the moment. The only thing you will have to watch for is email responses to parts enquiries. Bob’s BMW are great for parts, prices and phone service (when you can get through, but there email response (to me in Australia at least ) has been non-existent. Motorworks & Motobins in the UK are great and so is Munich Motorcycles here in Perth, Australia are good too. I can also recommend the POR 15 products. My tank looked OK but after sloshing some water around after cleaning the taps, a LOT of the tank paint came out…My advice though with the PORs tank relining kit is to either purchase the kit and a second tin of the paint or get each of the component products, picemeal and buy larger sizes. I found the paint to have a very low viscosity ie too thick and it didn’t cover all the internal of the tank. Even used the left over from the first attempt and still missed bits. The second small tin cost almost as much as the kit. Finally don’t forget to check BMW parts availability – pannier bits are nla in Oz, and Real OEM for the parts pics.


  8. SlowJoeCrow says:

    I have a 78 R100S, successor to the R90S so I’ve done quite a bit on these. The seat you have is actually the standard seat for an R90/6 since these were the basic touring model. The seats with the cowling were only standard on the S, RS, and RT models in the 70s. Also the lathed down socket in the toolkit is probably a 27mm used to torque the swing arm bearing locknuts. The clearance is very tight, but the torque is low. I recommend Eurotech for general parts and also Rocky Point Cycle for upgrades, he carries Boyer Bransden electronic ignitions, Epco exhausts and stainless fastener kits.

  9. Bill of WI says:


    jaysusmerrynjoesuf !!!!

    Even I could do….sigh….

    how’s about moving along, here, Buddy?


  10. luthier58 says:

    My wife would point out that I have no room to talk, but it would be nice to get back to this project.


  11. Maybe it is time to offload this project to …well…..ME??? I have done 2 others from ground up….What do you think??

    Rocky McCumber
    Reno, NV

  12. Darkstar N.H.,USA says:

    I bought a 1979 R100T last summer with 24k miles on the clock.
    I’ve been doing a rod bearings on up resto job on it this winter.
    Old bearings looked very good but put new cause I was there.
    Spines not looked at for 29 years.
    They turned out to be fine but dry.
    I’ve got to get it in gear to finnish up shortly as warm riding days are here shortly.
    Got’s to go pump out the cellar.
    Don’t want that beautiful BMW to get wet!
    I got pictures for anyone interested.
    Let me know.
    Happy puttering!

    Fred R.

  13. Ron H. says:

    Hey Fred,
    I am trying to get a 79 R100T going as well. Would love to see your pics. You can check mine out at bmwmoa.org in forums and do a search for Does this Airhead make me an Airhead”

  14. e46 led says:

    People could find those rims on the E46 that has the competition package. As for the tail light changes, this is the low-cost tactic of delivering a small refresh into its latest design to fascinate buyers into getting a newer model year. They do it on a regular basis with the front skirt and taillights. The E46 didn’t attain it’s taillight upgrade until the late 03 styles I think.

  15. Lawrence says:

    Just been going through the archives to see if this project was ever continued. Turns out they parted her out due to lack of time. Oh well, I was looking forward to a nice breakdown of a restoration.

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