Bringing 74 R90S back to life after sitting 30 years

Discussion in 'Airheads' started by _cy_, Sep 30, 2011.

  1. _cy_

    _cy_ Long timer

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    Bringing 74 R90S back to life after sitting since 1979 ... parked with only 7,300 miles on the clock.
    purchased from the original owner's son. This bike was the 41st R90S made to USA spec's off the assembly line. one of the first R90S to hit American soil and quite possibly the lowest mileage un-molested R90S in USA.

    Was torn between selling this bike, purchasing a modern bike with proceeds and keeping it.
    At first I thought it would be a shame to put mega miles on this R90S. But came to conclusion, that's what it was made for.

    After thinking about it for a day.... nah... more like an hour... keeping the R90S!
    It's my goal to bring this bike back to 100% mechanical condition. reliable enough to tour.

    This thread is to document the process, that is if anyone is interested...

    30 years of dust
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    #1
  2. opposedcyljunkie

    opposedcyljunkie Heavyweight Boxer

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    Nice find and good decision to keep it!
    #2
  3. _cy_

    _cy_ Long timer

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    tires were leaking so pulled down front tire, only to find natural rubber tubes inside are in perfect condition. valve stem was leaking.

    need help in deciding which tire to put back. Bike came with a brand new Metzler 3.25 x 19 tire still wrapped. what shall I do? find a modern tire to install and put back the original Metzler or just install the new Metzler?

    will need to fabricate a tire balancing tool with bearings. best tube I could find locally was a Japanese made IRC brand.

    after replacing valve stem in rear tire, holding air fine.rear tire appears to be pliable, looks & feels like new. will leave it alone for now.

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    #3
  4. DoktorT

    DoktorT BigBrowedNeandereer

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    What a great project. Getting to safe and reliable for use is a worthy goal. I see a two stage process. First stage is partial dissassebly for cleaning and inspection.

    Safety means new tires and tubes.

    A through cleaning of tank, petcocks and carbs is required for reliability. Do that once right and be done with that. Do pull the front cover. Go over all the wiring terminals under there as well as the headlight pod and under tank area. Clean and tight everywhere.

    Just standard maintenance elsewhere. Valves, oil and filter, lube, splines, head bearing and swingarm tension, the basics. New battery then just test all lights and switches.

    Flush and renew the brake fluid, then pull the handle as hard as you can and verify firm and no leaks. Rebuild master and calipers if required.

    Then you can fire it up and test drive, tune the carbs.

    Stage two is to put a few hundred miles on it and see if you got some leaking seals somewhere and monitoring for proper function of all systems.

    Sure hope it wasn't stored with gas in the tank and carbs.
    #4
  5. Detroit Steve

    Detroit Steve Homely Adventurer

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    DOKTOR T is right but left out one thing.


    Clean and repack ALL bearings! the grease that was ok back in the day will be the consistency of candle wax today.


    Enjoy that bike you lucky devil!!!!!
    #5
  6. DoktorT

    DoktorT BigBrowedNeandereer

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    Covered under basic maintenance I did mention. That includes everything listed under maintenance in the factory manual, including the wheel bearings and LOTS of other things I. No need for me to be redundant to exhaustion on this.
    #6
  7. elite-less

    elite-less Been here awhile

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    Great base for a project! I'll be checking on this.
    #7
  8. _cy_

    _cy_ Long timer

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    thank YOU!

    this is exactly what I need. don't know if fuel was drained. after sitting that long, it's completely dry.
    who knows, I could get lucky and find everything completely clean and ready for fuel. will know after tearing into carbs. if fuel bowl is full of gunk, then everything is getting flushed.

    didn't catch the part about repacking bearings as this is my first BMW and are not familiar with scheduled maintenance yet.

    brake master cylinder needs to be replaced or rebuilt. I'd do that even if was working perfect. calipers are not leaking, so leaving them alone.

    notice the entire engine is painted black, not just cylinder base. this was pointed out to me by several Adv members already. No question this was done at the factory as engine has never been out. all the factory tie straps are still intact.

    don't know but speculate that when BMW factory was setting up assembly line for USA spec bikes. first few R90S got a few things done to it that rest of this model run didn't get. Serial # 4950041 matches on engine, frame and ID plate.
    #8
  9. kraut.burner

    kraut.burner "Fun Club" President

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    subscribed :lurk
    #9
  10. Renner

    Renner rockin' the toaster

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    subscribed :lurk

    Where-abouts are you located?

    We're having a tech day here next week... though odds are pretty slim that you're close enough to drop by for a visit.

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    #10
  11. _cy_

    _cy_ Long timer

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    located in Tulsa, OK ... hope to visiting a few Adv riders around the country in the near future on R90S.

    sure wish I was closer to attend... does anyone know if slightly higher compression engine 9.5 to 1 still will run on regular? no problems getting premium in US. but I suspect down south, one runs what's available.
    #11
  12. Renner

    Renner rockin' the toaster

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    You'll likely get good responses on this.
    My take is no, not very well... better if you retard the timing.
    You might give it a try and see if it pings (which it probably will, especially under load/hill climbs), but much pinging would be quite detrimental so go easy.

    Pretty sure our current premium is lower than the factory recommended octane for your R90S but I don't have the operators manual on hand.
    in other words, best to run the highest octane available.
    #12
  13. ooweel

    ooweel Jobless, Its OK!

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    You are not allowed to post 74 90s pics with out including pics of the mirror stalks. :lol3
    #13
  14. east high

    east high Been here awhile

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    Me too! BTW, Isn't this the second 'hey check out my original r90s' thread in as many weeks? Lucky sods :D
    #14
  15. jackd

    jackd Long timer

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    Lucky you on finding this bike. As to your question on the need to use premium gas in your bike. A Triumph T100 that I restored had a compression ratio of 9:1 and I ran it on today's premium. If I really loaded it, it would still ping on occasion, so I made damned sure I never used regular gas. Seeing as your RS is 9.5:1, I would not even contemplate using regular gas. You have too nice of a bike to go for the less expensive grade of fuel. Put the additional cost of premium fuel as one of the expenses that come with owning a premium bike.
    #15
  16. caponerd

    caponerd Kickstart Enthusiast

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    Good find.

    You have to wonder why it got parked after only 5 years of use? Based on where some of the dust is located (didn't just settle there out of the atmosphere), those were possibly a pretty hard 7300 miles.

    I hope you don't find any disasters hiding inside the engine!

    I run only premium in both my old BMW's; R100 and R69S. Whenever I'm able, I stop at a gas station near a local lake that's popular with boaters and buy non-alcholhol blend premium.
    They'll fill motorcycles, old cars, boat motors and garden equipment, but not modern cars and trucks.
    #16
  17. _cy_

    _cy_ Long timer

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    question about running premium fuel is not about costs, but where R90S is limited for touring fuel wise. remote parts of the world where I'd like to go eventually, one cannot be picky about fuel.

    the story as told to me by the original owner's son. when the baby arrived, mom told him it was the bike or the kid. so R90S got parked. the son has never seen his dad ride the BMW ever.... he's 30 years old. he told me repeatly, his dad LOVED that bike!

    the R90S was stored inside a large shed in his back yard all these years. all the oxidation is from 30 years of 100f summers and below zero winters. Original owner was a Electrical Engineer with American Airlines. My feelings is he babied the R90S the 7,300 miles it was ridden.
    #17
  18. fishkens

    fishkens Long timer

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    Nice find of a great bike. :thumb

    I'm curious about the engine case, trans, etc. being painted black at the factory. Is the original owner still around to confirm? Has anyone ever heard of BMW painting the cases black (before the K-bikes)? Just curious.

    Any mods other than the rear rack?
    #18
  19. _cy_

    _cy_ Long timer

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    no other mods that I'm aware of ... rear rack is the only piece I can find that was added.
    unfortunately seller's dad passed away last year.

    there's is NO way that engine got painted black without entire motor being out of frame. all indications are this bike has never been apart. factory plastic straps are intact all over bike's frame.

    every single picture of any R90S, that I've been able to find or heard of all have silver engine bodies????

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    #19
  20. fishkens

    fishkens Long timer

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    Agreed, that's why the black paint is curious. Given that the PO was an EE I imagine he may have had the patience to R&R the engine to paint it and reassemble it perfectly. Or, the engine may have been painted in the frame?

    Are the white stripes on the timing cover bare aluminum or painted. Just wondering if that's what the pin striping tool was used for.

    Regardless, looking forward to seeing this bike cleaned up and on the road.
    #20