First Airhead: 1975 BMW R90/6 project. Help needed.

Discussion in 'Airheads' started by BeachZack, Sep 6, 2012.

  1. BeachZack

    BeachZack Adventurer

    Joined:
    Sep 4, 2012
    Oddometer:
    12
    Hey guys, I'm Zack, been browsing the forums here for quite awhile now and finally made an account just as I picked up my first real project, a 1975 BMW R90/6. It runs, and I was able to test ride it, but it does need some work before it's ready for the road.

    Things it definitely needs are:

    New battery - Recommendations?

    New plugs

    New fluids - do you guys run synthetic motor oil or should i stick with regular?

    Carbs need to be cleaned, the gas was pretty old in it.

    The tank needs to be cleaned out and resealed, I've seen a thread somewhere detailing exactly what to use and do, but I cannot seem to find it now when I need it.

    The rear shocks have cracked on top, I don't think it's a big deal right now, but something to replace before I ride.

    The throttle seems to be a bit "sticky," it doesn't get stuck open and does close when i take my hand off it, but opening it definitely isn't as free as I would like it to be. Any ideas?

    Some of the wiring needs to be sorted out, the front left signal was the only one working, and the brake light only goes on when I use the rear brake, not the front


    Less importantly, the bike has Lester 7 spoke wheels that I'm not particularly fond of, where would I find a good set of wire wheels to replace them?

    The previous owner put the fork gaiters on the rear shocks, and they are now pretty torn up, I like the look of them and would like another set, where do I buy these?

    The bike has a "roll-off" stand, but I think the stock center stand would be a bit more convenient to work with, and I'm sure I'll figure out how to rock it forward and go in one motion.

    I'm not sure where I'm taking this project at the moment, but just out of curiosity will a /5 toaster tank fit this bike? :evil



    This is also my first ever "build thread," I'll do my best to keep it as updated as possible with as many pictures as possible, please excuse any stupid questions, I have a lot to learn.

    9/06/12
    Today is the day after I brought the bike home, what I've done so far is started taking the bike apart, removed the gas tank, seat, luggage racks, fenders, etc.

    [​IMG]

    First stupid question: are there supposed to be screws in the valve covers here?

    [​IMG]

    And a picture of the crack on top of the rear shocks, this one is the worst of the pair.

    [​IMG]

    I think that's pretty much it for today, thanks for reading.

    Zack
    #1
  2. disston

    disston ShadeTreeExpert

    Joined:
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    There is a stud in the cylinder head that has a cap nut on it holding the valve cover on. The threads in the head get stripped and the stud pulled out. You can fit a regular nut into the space behind where the stud bottoms out by grinding two opposite sides of the nut down enough so it fits here. You can also Heli Coil the part where the original threads were. Your choice.

    So the valve cover is held on by the center std and on the back side there are also two smaller nuts at both ends. I think this is explained in a manual. You need a manual.

    Dinosaur oil.

    Do you live near a dealer to buy some plugs over the counter? Use non-resister plugs. What plugs are in the bike now?

    POR-15 for the gas tank.

    Throttle cables on BMWs are not lubed. Don't lube them. You might need new cables.

    Use the stock airfilter. The stock oil filter. Stock plug wires have 1000 Ohm caps. The fork gators work better on the forks. They protect the fork tubes from stone chips and debris. Buy new gators at the dealer or where ever you are buying parts from.

    Where are you?
    #2
  3. BeachZack

    BeachZack Adventurer

    Joined:
    Sep 4, 2012
    Oddometer:
    12
    Thanks for your reply, I'm near Los Angeles, I'm sure we have a dealer around here somewhere
    #3
  4. Padmei

    Padmei enamoured

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    Location:
    Nelson New Zealand
    #4
  5. _cy_

    _cy_ Long timer

    Joined:
    Sep 25, 2011
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    Tulsa, Oklahoma
    unless you are already used to working on bolts threaded into aluminum. take extra care not to over torque anything. look up torque spec's, when it says 6ft lbs, it means it.

    chase down a factory workshop manual, if you don't already have one. a Haynes manual is also worth having.

    check out the airhead section, find the tips and dark secrets threads. lots of folks willing to help...
    #5
  6. tete

    tete clown shoes

    Joined:
    Oct 15, 2009
    Oddometer:
    346
    Location:
    Gilbert Az
    welcome,

    Im fairly new here so I will do my best with information provided by others to me.

    Listen to them, they know what they are talking about. I got the Clymers manual over the haynes as I am the type of person that appreciates pictures. Clymers is very detailed, haynes is good but IMO Clymer is the way to go.

    I would recommend taking the carbs apart and cleaning them thoroughly. I have succes with non abrasive cleaners like Simple Green. Soaking them overnight

    gets them nice and clean. Also use the seafoam where everyone recommends. My bike was sitting for ten years and the gas turned into honey in there. Making the butterfly super sticky as well as just clogging everythign up .

    In my opinion, I would take it all apart and doing it properly as in the long run it will save you money and headaches. It will make it difficult to tune with it all gummed up.

    Most importantly it may save your bike from any serious damage.

    I would also considering ordering from eubmw.com as they seems to be priced right and quality goods. it is recommended here in the sticky thread about dark secrets. These bikes I am finding are actually pretty in-expensive to find parts for , and ther eis an abundance of them avaialble. There are generally lesser expensive solutions if you know where to look.

    i am expecting my SLA battery tommorrow. it cost me about 40$ I'll let you know how that goes befoer i give any advice there. Certainly the dealer battery is an option if you're rich. it runs about 130-140$ other options like optima, from what I have heard / read, is probably the best but once again you ar elooking at $140 or so.
    SLA battery should be smaller and pack enough punch if it works as expected.

    Order new cables and hoses. I am new to BMW Airheads but with my hondas in the past I always found not to flinch here. Just order them and be done with it. Same goes with tires. If yours are bad, get new ones like your life depends on it, because it does.

    All cosmetic stuff is your call, gaitors, shocks, tank etc.. use the flea market here and barter stuff. Your bags and luggage racks will get alot of interest. Trade or sell if you don't plan on using them, and use the money on that toaster tank and other goods.

    I have lesters but they are a bit different than yours. I like mags but if you really want that vintage look , spokes are the way. You may want to look into relocating the master cylinder at the handlebar. Im not sure what it take on a /5 but I can't imagine its that difficult.


    THIS IS BY FAR THE BEST FORUM IMO. The people here are respectful, helpful, answer quickly, admit when they are wrong and most importantly experienced with everything you are going through.

    When it comes to working on these Im all thumbs and even Im starting to feel confident.

    Easy thign to remember is its all jsut nuts and bolts. There is no magic.
    #6
  7. merge87

    merge87 Adventurer

    Joined:
    Feb 24, 2012
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    Someone may correct me but I believe a standard /5 toaster tank will not fit your r90 because of the under tank MC. But if I remember correctly there's a way to modify those tanks to make room, or go through and switch to a handlebar mounted MC.

    All that said...I very much like the look of the /6 tanks. I could be biaed because of my r90 of course! Did yours come with the small or large tank?
    #7
  8. daveoneshot

    daveoneshot Been here awhile

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    Dec 14, 2010
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    Vermont
    Don't forget Hans Lowe at Hucky's BMW Parts. Google him up and check out his site, better yet, give him a call and speak with a true connection to the Fatherland. He knows his stuff.
    #8
  9. disston

    disston ShadeTreeExpert

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    Silver Spring, Md
    You would have to move the MC to the handlebar to use a Toaster Tank. Not a bad move, it's an improvement for the brakes. But Toaster Tanks are expensive, If you really like the tank get a /5???

    The /6 Large tank is my favorite BMW gas tank.

    You may prefer to buy parts from any of the many sources but I just think it's a good idea to drop by the dealer once in awhile. Many of them are not very well stocked with Airhead parts but most of us do try and support them. Really depends on who your local dealer is. Mine is fantastic and he not only supports parts and service for Airheads but you can have any BMW ever built worked on at Bob's. He also has a Museum on the grounds. It's too bad there aren't many like him but I do want to encorage the ones that don't support Airheads to do a little better.

    I also like Hans Lowe at Hucky's. You do have to call him. He doesn't take orders over the interwebs but his system does work and he is a big favorite.
    #9
  10. merge87

    merge87 Adventurer

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    Agreed!
    #10
  11. rebelpacket

    rebelpacket four-stroke earth-saw

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    Oddometer:
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    Location:
    Missoula, MT
    Drop all the fluids, and maybe the oil pan just to check for bits of badness or grit. Looks pretty solid though!

    Was it a daily rider? Or just a bike that was sitting for while that the PO got running one day for sale?
    #11
  12. BeachZack

    BeachZack Adventurer

    Joined:
    Sep 4, 2012
    Oddometer:
    12
    Thanks for the advice everyone,

    It definitely has sat for awhile at one point or another, the original owner owned it for most of its life, but after he sold it I think it got a little less care.

    Also figured out that the tank is actually in pretty good shape internally, what i was seeing is just BMW's sealant. :D
    #12
  13. bmwhacker

    bmwhacker Still on 3 wheels

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    MONTANA NATIVE from NATIVE MONTANA
    I'd shy away from synthetic oils unless you're going to rebuild everything with new gaskets / seals.
    I went to a semi-synthetic oil in my /5 years ago and a couple tiny oil "weeps" became major oil "leaks" within a 100 miles.
    #13
  14. BeachZack

    BeachZack Adventurer

    Joined:
    Sep 4, 2012
    Oddometer:
    12
    Ok, the bike is now mostly stripped down, all that's left is the forks and triple trees, then it's time for powder coating.

    As for the engine, what is the best way to clean it up? I don't want it to shine, just want it to look how it did when it left the factory. How can I get the grime off and bring it back, then preserve that?

    [​IMG]
    #14
  15. Brun

    Brun Been here awhile

    Joined:
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    537
    Location:
    BorderBurg, South East Oz.
    Clean your alloys with a solvent and a kitchen scratchie (Scotchbrite or similar). The castings have pores that fill with black grime. Best treatment I've found is Rub'n'Buff. A little 15ml tube will do all the alloys from a couple of bikes.

    [​IMG]

    Just rub in a small amount with your finger and buff off with a rag. It leaves a waxy film that apparently lasts a long time.
    RnB comes in different colours. The one used above is Pewter. Lots of folks use Silver Leaf for a brighter appearance.
    #15
  16. US_Marshall

    US_Marshall Adventurer

    Joined:
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    Ct
    I like "Simple Green" to clean of the oil residue. For the heavy stuff you might want to get a plastic scraper so you don't damage the aluminum.
    #16
  17. tenderfoot

    tenderfoot PRJ

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    Gauteng, RSA
    My bike also came without the centre nut for the tappet covers, luckily the thread was OK and I simply took a length of threaded bar (8mm ?) screwed it in untill it bottomed against the head and sawed it off at the correct length. The nuts are quite expensive and the torque is so low I suspect they are largely cosmetic, the two back nuts do the job quite well on their own. Someone will definitely chime in calling for my head on a platter for this heresy :lol3.
    #17
  18. rebelpacket

    rebelpacket four-stroke earth-saw

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    Missoula, MT
    I use kerosene and a paintbrush to clean off the porous metal surfaces. Then some simple green or equivlent to remove the rest of the kerosene. I like the buffing option though, those alloys look beautiful.
    #18
  19. BeachZack

    BeachZack Adventurer

    Joined:
    Sep 4, 2012
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    Yeah I'm sure its not big deal and if they really are stripped I'll put in a helicoil

    I've heard that simple green is corrosive to aluminum, any problems with doing this?
    #19
  20. tete

    tete clown shoes

    Joined:
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    Gilbert Az
    If this is true then my entire bike should be falling apart soon.

    One thing I have always had succes with is simple green. It's not really the fastest way but has consistently been the safest least abrassive approach.

    I can say with a certain amount of confidence that I have no / zero data supporting my claim except for my own experience using it on 3 bikes now. :rofl
    #20