Thoughts on a 1975 BMW R90/6?

Discussion in 'Airheads' started by QCDStick, Apr 10, 2012.

  1. lmyamen

    lmyamen Been here awhile

    Joined:
    Nov 29, 2011
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    Des Moines, IA
    My R90/6 working through just a few small issues and it should be perfect. Did the restore over this winter..Just put some love into the bike and you will not regret it!

    What is looked like when I bought it.

    [​IMG]

    After 4 months of work this is what I ended up with!

    [​IMG]
    #41
  2. More_Miles

    More_Miles ├╝ber-n00b

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    I'll let a more experienced Airhead wrench/guru chime in here, but it sounds like the head gasket is shot where top end lubricating oil comes through the channels in the cylinder. Head gaskets aren't THAT expensive. But buy the damned exhaust nut wrench and a bunch of penetrating oil. You'll need the wrench to fit those finned nuts and the act of having the penetrating oil will mean the nuts won't be seized/galled to the threads on the head. BTW, there is a right way/wrong way to put them on. Can't remember off the top of my head which is which.

    Which brings to mind, I'd suggest asking your grandfather if he has any of the special tools like the exhaust nut wrench or any of the other myriad of "special/modified" tools for working on the bike. They aren't hard to source, but if he already has them, well, no sense in breaking up the set.

    One "quirk" I'd suggest you nip quick, especially considering the age and recent usage history, are the front and back wheel bearings. They are automotive style wheel bearings and unlike modern motorcycles, are DESIGNED to be serviced. Disassemble them, clean them, inspect them, reset the bearing pre-load if you're anal, obsess over it if you're super anal, pack them with fresh grease, and put new seals in them. Figure on doing this every couple of tire changes. Spun inner journals welded to the axle isn't fun. DAMHIK.... :deal Spun races and destroyed hubs is even less fun.

    The bike will drive you to distraction with things like the electrical system (what were they THINKING? Taking lessons from Lucas?) to the side stand (what were they THINKING? Way out under the cylinder so you can't SEE it?) to the centre stand (what were they THINKING? Do you see a pattern developing here?) But I must say, until I got the airhead, I never had a bike that made me want to throw a leg over and strike out for California from New Brunswick/Maine just because...
    #42
  3. disston

    disston ShadeTreeExpert

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    Your Grandfather should have some tools especially the finned exhaust nut tool. Every Airhead rider has to start with getting this tool. Well almost every one. But you will use this tool again and again. So if Granddad doesn't have the tool there are several sources and thru the years there have been many versions of this tool. We will advise, but right now there is an original one on Ebay that has not been bid up yet. These go for a pretty penny sometimes. I don't want to tell you what it might be worth they are sometimes over priced I think. But I do like the original heavy BMW tool.

    http://www.ebay.com/itm/270955014898?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
    #43
  4. QCDStick

    QCDStick Adventurer

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    My grandpa does not have the tool. I specifically remember him mentioning taking it to a guy he knew when he needed that. I checked out the Ebay thing, but seems someone else has a relativly high max bid already on the item. Not sure how much I should pay for it? As it sits now, still outbid and it's 30 bucks shipped right now.
    #44
  5. disston

    disston ShadeTreeExpert

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    If it goes no higher then somebody got a good deal but no telling how high it might go. I can tell you I've seen these sell for over a hunnert on Ebay. I do think that is too much to pay for most people. They might still be available but I haven't seen any other than the auctions for some time. I think the last one I saw new was still 70 or 80 bucks but I'm not sure about that.

    I don't even remember what I paid for mine 30 years ago. But I still have it.

    At this point if you wanted to try and win this item don't bid any more but "snipe" it. I use a service called Gixen. You can find them with Google easy enough.

    That wrench is the cast iron one. There is also a cast Aluminum one that I don't have but think they look OK. Max BMW sells the Aluminum one pretty cheap;

    http://www.maxbmwmotorcycles.com/fiche/PartsDetails.aspx?source=catalog&diagram=ST_EXHAUST WRENCH

    And there is one sold by Cycle Works that works with a half inch breaker bar.

    http://www.cycleworks.net/index.php?main_page=product_info&cPath=29_33_51&products_id=346

    I think most recommend the Cycle Works wrench and it also has the big advantage of being small enough and light enough to sometimes be carried on the bike.
    #45
  6. Jim K in PA

    Jim K in PA Long timer

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    Great bike. Glad you are taking it. I think those panniers are the narrow "city" cases - pretty rare. The lighting was added, I strongly suspect.

    My R100T had a windjammer on it when I got it. Removing it was the first thing I did. No regrets. :D

    Check out www.northwoodsairheads.com for basic tools and parts. Jeff Trapp is an inmate here. I got the exhaust nut wrench from him as well as other bits like head gaskets, etc.

    Keep us posted on your progress.
    #46
  7. QCDStick

    QCDStick Adventurer

    Joined:
    Mar 26, 2012
    Oddometer:
    12
    Updated picture:

    [​IMG]

    Set aside the panniers, installed the new headlight, and a little simple green. Still a lot of grime and dirt, but it's already cleaning up surprisingly well!

    Now, if only this rain would stop...
    #47
  8. Hawk Medicine

    Hawk Medicine Coyote's Brother

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    Jun 8, 2008
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    Location:
    NOR CAL
    Heres a shot on my 1976 R90/6 in 1985 at the Delaware Water Gap ,a few days after buying it and heading out from Va Beach to Canada:

    [​IMG]

    Same bike a couple of years later at a rally in NC.

    [​IMG]

    Here it is about three years ago after a little work:

    [​IMG]



    As far as I'm concerned, the R90s represent one of the true high points of Airhead development because the guys in Germany got so many things rght. Good power, good fuel economy, pretty smooth and there are plenty of things that you can do to make em runn good and last.


    PS: My old R90 engine just loved to cruise at 80 to 85 MPH and would returm 40 or more MPG. These days my bike is equiped with an R100 engine and I like it but the R90 was very special! I'm glad that you shucked that fairing but if you decide to swap seats, make sure you keep that double bucket. Theyre great for long distance riding.

    Take care of Grandpa's bike. You'll love it!!
    #48
  9. targabill

    targabill no_guts_no_glory

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    May 18, 2008
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    I have 64/32/11 and 64/32/12 carbs on my 75 R90/6 they do not have slide spring above the diaphragm, are they supposed to be there? What would happen if there missing? Where can I buy...

    thanks, Bill
    #49
  10. chasbmw

    chasbmw Long timer

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    the springs are available from the usual sources, check snobums site for part nos.

    i have fitted them to my R90/6 but still need some work on rhe carbs as am suffering from slow speed surging in city traffic.
    #50
  11. disston

    disston ShadeTreeExpert

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    I also have an R90/6. Mine is 1975. It's not as pretty as a lot of these machines you guys have but beauty is in the eye of the beholder, ya'know. Those are the stock carbs you have and I also am running stock Bing carbs. Most everybody says adding the slide top springs is an improvement in carb response. I have them also. And it may be an improvement.

    There are two versions of the carb top springs. The earlier version is a stiffer spring and the one you want is the later. The later one is thinner wire and not so stiff. Here s the number of the stiffer, early, spring; 13 11 1 335 324

    The one you want is ; 13 11 1 338 134

    They are not really very expensive, less than $20 for a pair. While there consider new screws for the carb tops, those get buggered up over the years and Stainless Steel is available. Use a little AntiSeize on them.
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    #51
  12. mfp4073

    mfp4073 Long timer

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    It is my understanding they did not come with the springs, but could be added later to correct issues like the slides hanging up due to wear.
    #52
  13. bjames77

    bjames77 Adventurer

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    Great thread. You'll love it when you get it all sorted.
    #53
  14. mfp4073

    mfp4073 Long timer

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    [​IMG]


    adding new gratuitous pic to the thread!
    #54
  15. BMdummoyou

    BMdummoyou Adventurer

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    SPringfield il
    I have owned and ridden many bikes, a couple ducatis a 72 triumph and burned through some turns on the latest crouch rockets. But all that I can say is that an old airhead is on another level, it does not "feel" like you are going 100 down an open stretch of road but you are and cornering is insane with that high center of gravity and the first thing to scrape the ground isn't your pegs or muffler, it's your valve cover, and let me tell you, you are close to vertical when that occurs. When I first really committed to a corner on my 74 r90 I was more scared and excited than on any other ride I had previous or since.

    The only reason that I own mine was that I was desperate for a bike under 3000 during a certain part of my life and picked mine up for 2000. The guy I got it from was clearly sad to see it go but was moving on to less adventure. Best purchase I have ever made, hands down. Reliable, bulletproof, utilitarian, cool, and fun! Best bike I have ever owned hands down.

    Oh and the size thing, I look like an ape on most everything I have ever ridden being 6'4" and 240 but this bike is great for my stature.

    You are not going to outperform everyone on this bike but you will definitely have the most fun of anyone trying!
    #55
  16. squish

    squish Out of the office.

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    Location:
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    Just last night we stopped at the grocery store and out front was a very tidy R90/6
    Had GS bars Hella bar end winkers, and the older style bags, along with the larger fuel tank.

    Had a very decent and purposeful look about it.

    And a new rider aboard it who was more then happy to chat about it, nice to see people getting into riding these beasts.
    #56
  17. ChristianJS

    ChristianJS Adventurer

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    Mar 25, 2012
    Oddometer:
    30
    Mine should be out of the shop today. A couple months of messing around to get everything dialed in. The weekend looks good, so I'll be logging my first set of real miles on it. I love the look and the initial few test rides I took.

    [​IMG]
    #57
  18. dougsdrive

    dougsdrive Purposely Lost

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    Very nice looking bike! Thanks for sharing. I'd love to take on a project like this. Where can I get a seat like this?
    #58