Back on an Airhead - 1975 BMW R90/6

Discussion in 'Airheads' started by tete, Aug 27, 2012.

  1. tete

    tete clown shoes

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    The konis look to be in fine shape. Everything was stored away very neatly. And well taken care of. This was by no means a barn yard find.
    #21
  2. Horsehockey

    Horsehockey A GPS? Huh?

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    The tank looks like a /7 or later to me. Might end up with a gap between the tank and seat, but not sure. A version of the larger tank is desireable over what you've got (4.5 gals or so), so I'd check fitment and then decide whether to sell the tank. The gas cap you show should fit the tank - but just leave it off for now - we can discuss stuck gas caps later. Your mirrors are, I think, the longer stem OEM mirrors that you would use if you mount your S fairing. Can't tell what's in the little plastic bag, but I'm not seeing the mounting hardware for the fairing. You really need that hardware to get serious about mounting the fairing. The voltmeter and clock are the "green faced" later versions: not OEM for your yeargroup, but they'll work fine and will fit in the S fairing fine. Can't really tell, but the Koni shocks look pretty good - the 7610's were stock for that bike and are great provided they're not worn out. I'd keep that front fender - if it's correct for your bike, you might want to eventually paint it and replace the existing front fender which a PO did a bodge job on with mounting the brake line bracket (incorrectly) to it.

    The pump mounts under the seat on the driver's side subframe rail - you'll find a little mounting peg there.
    #22
  3. Foot dragger

    Foot dragger singletracker

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    I brought a 76 /6 back from the dead once,I dont think it was much over 3500.00 before it was at the point where it needed cosmetics and a top end rebuild/timing chain/look at the gearbox. Its probably best to cash out the children's college fund now.:rofl
    #23
  4. tete

    tete clown shoes

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    There looks to be plenty of additional hardware not pictured. I would assume the stuff bundled with the fairing and gauges all work to mount it up.
    #24
  5. disston

    disston ShadeTreeExpert

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    It looks to me that somebody was building themselves an R90S from an R90/6. Have you run the serial number yet to see what it really is? If in fact it is an S bike it is a primo score. But like I say I think somebody was building an S bike which is still a nice deal to do.

    Run the 7 digit # stamped into the head stock and checked against the number above the dipstick hole on this site; http://realoem.com/bmw/

    The R90S tanks look like the /7 tanks and they might be but I think there is some minor difference. It fits like a /7 tank anyway and will match that seat frame you have once it is finished, need a little more parts collecting. If you use a /7 tank with a /6 seat, what you have now, there will be a larger gap between seat and tank. That's doable though.

    The front fender is a /6 not an S fender.

    You have 90% of everything needed for this mod. Will need the parts to make a dual front brake set up. But most of the serious money has already been spent. If you have a different vision or want to go in another direction there's money in those parts.
    #25
  6. tete

    tete clown shoes

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    using the website RealOEM.com it states the bike is a R90/6 manufactured 5/75.

    So if I understand you guys correctly for the best fitment with no modifications are:

    If I use the R90/7 tank then I should use a R90/7 seat as well.

    and or R90/6 tank and R90/6 seat.

    This would result in a seat and tank combo with no gaps.

    Either way it should be a simple bolt on / Slide on affair ?

    I don't see myself using the fairing. or those gauges so if any of you are interested feel free to shoot me an offer. I will also post in the thrift section You will have to guide me through the hardware, as I am sure it's there just would have to account for it.


    I don't care for the R100 cowl seat frame as well.

    I haven't decided about the saddle bag / case mounting hardware yet.

    The wheels I actually like. I generally hate mags, as most my hondas have wire wheels but I think the mags will add a more aggressive look. I have to find out if these Lesters can be ran tubeless.
    #26
  7. tete

    tete clown shoes

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    I went ahead and remove the oil today. I figured this would at least begin to tell the story of the bike. To my surprised the oil looked relatively fresh. not black at all and didn't have a chemical residue or anything that would indicate any breakdown.

    I also went ahead and removed the float bowl to see how it would look.

    Once again I was pleasantly surprised in that it wasn't as bad as some of the bikes I have worked on in the past. As a matter of fact everything look really good and moved freely. The gas had not turned to gel by any means.

    [​IMG]
    [​IMG]

    also I was looking at my seat and I am starting to wonder if I already have a /7 seat going. there seems to be a large gap on the seat tank meet - see attached.
    [​IMG]
    [​IMG]

    SO far I'm actually please with what I have seen and think this will be running much sooner than later.

    I have a carb rebuild kit coming and then a battery. Then I can start electrical to find if it really is the starter.

    I also visited a BMW mechanic and he said the starters on these bikes are really heavy duty and more than likely something else failed.
    #27
  8. Bigger Al

    Bigger Al Still a stupid tire guy

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    You gave up too soon. :deal










    :hide
    #28
  9. Bigger Al

    Bigger Al Still a stupid tire guy

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    Just for future reference, there was no R90/7, but rather an R100/7. Not a big deal, but it might help figure out what you need with less effort on your part.

    The silver tank is from a /7, and is longer, hence it won't fit with the smaller /6 seat that is on the bike. You can find used seats pretty easily, and the prices are all over the map due to condition and such.
    Once you have the matching /7 stuff it will just bolt/slide on.

    You can try to fit the other tank and your current seat to see it things match up. One of the nicest things about an Airhead is that they're easy to work on.

    You'll get a metric shit-ton of opinions about running the Lesters and early BMW mags tubeless, but it's not a good idea. Neither wheel comes with a safety bead that will help keep the tire in place in the event of a flat, and the Lesters are known to be pourous at times depending on condition. Running tubes can be a PIA, but in this case it's the safest option.


    I swapped my starter out to a newer model Valeo from Euro Moto Electric, and installed the Odyssey PC680 battery. My bike has never started better. Again, you'll get varying opinions on the quality of the Valeos, and there is nothing at all wrong with rebuilding your current Bosch. Once done it'll last a long, long time.
    #29
  10. tete

    tete clown shoes

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    Thanks I'll look into your setup. The key here is to do this once and move on. Get the right battery and starter set up first time around. Also is there replacement electrical kits that are know to eliminate alot of the electrical bugaboos that exist? I'd like to knock it all out at the same time if possible.

    Sold my other Honda. Flood gates just opened.
    #30
  11. beachmike1

    beachmike1 Adventurer

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    Gas tank drain..derust. Clean. Rinse. Treat with naval jelly. Rinse.

    Clean peacocks..replace seals and and o rings. Check
    Replace fuel lines.
    Replace plug wires.
    Rest timing
    Clean recap plugs...put a nice shot of penetrating oil in cylinders. Let air out then a shot of 30 wt
    Drain oil which is 12 years is crud.
    Refill with new oil.
    Fee stuck clutch.
    Install new battery.

    Clean water contacts you can get to.

    Replace tires..after 12 years they are junk...period tires have a lot of oil and other softeners I. Them that leave the system over time. Also with high ambient temperatures the elastomeric cross linking continues to take place. These two factors will remove grip to the point of a hock puck.

    Replace the tubes too.
    Grease the steering head and wheel bearings. Prop shaft and change rear gear ol. Lube all control Cale's. Change brake fluid and lube rear drum pivots in the hub.. Replace the rubber grommets in the shocks. Fork oils should be replaced.

    All fluids have a probe. The diurnal temperature differential pumps cool air in at nigh ..with moisture and hot air out during the day..any moisture will eventually hit the dew temp and settle not the guild and contaminate it...lighter fractions of the lube will evaporate. Leaving watery yucky stuff that is lousy for ube and
    Okay to drink.

    All lubricants age and collect dust.

    Whine this is done. Put in good gas with preservative:puke1 and all that crack with fuel off.and battery on a trickle charger.
    Listen for starter speed. It should not start as the plus are not in..you are luring the bottom end with no load. So this in 30 sec pulses for five min over one hour... The add plugs ..attaché leads turn on gas. Remove air filter. Use a squirt of starter fluid and start. Have a wet rag ready I case of fire. It sould start and run for a few seconds racing then runn regularly..there will be smoke.

    Oh clean out the exhaust before you start the bike. Critters live in those.


    Kaynthat was some money. But grease drips out ages and stops lubrcitabg
    #31
  12. tete

    tete clown shoes

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    This is exactly what I needed. I've been putting together a hit list of things I wanted to do. I think you just about covered it and then some. I'm starting to believe the PO actually filled it with fresh oil when he stored it. i will replace, fuel lines, inline filters, rebuild petcock, battery of course. The tank is surprisingly clean but will get a cleaning as well. all the proper end will get their attention in due time. I'm focused on making sure it can start/ run OK before I start dumping an extraordinary amount of money into it. Once I feel confident about that I will purchase tires etc.. plugs, rebuild kits, hoses and filters, oil can all be recouped in the event I have to part the bike out.

    I'm pretty confident this bike was stored properly. There is ZERO rust. And the oil was fresh. I was told that storing bikes with fresh oil is the way to do it properly. The PO was a bike mechanic I found out. had a complete garage and such but worked on this and his .............harley..... might explain the chrome. You woul dhave thought he would have drained the gas tho :huh

    I guess we will see.
    #32
  13. disston

    disston ShadeTreeExpert

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    I don't think I would replace plug wires unless they were out of spec. Measure with an Ohm meter. I don't think I would treat a tank interior with Naval Jelly unless I was going to line it with a liner, then the liner kits come with the stripper you need. But you are just tryin to get this bike fired up I think? This idea that people have about restoring a bike coming out of storage, just so they can hit the key and ride around the block, I don't get it. There are things to do but you are first just trying to get the thing running, and ride around the block. After that you will know more about what the bike needs.

    Any where there is grease you should clean and regrease. Check preload. If the bearings look OK then they are OK.

    Clean the tank with a garden hose, water. Get any and all crud out of the tank. If there is evidence of there had been a lot of flaking or rust passing thru the petcocks you may want to rebuild these otherwise you may decide to go with them if they flow well. Dry the tank with compressed air if you have it, otherwise make sure it is set in the sun and thourolly dry before reusing. I am talking about a basically sound tank. If you have Severe Rust or Pin Holes in the metal we will have to take more extreme measures.

    Sometimes you will want to rebuild the carbs or you may decide that a cleaning is all that's needed right away. If the carbs sat with fuel in the bowls they will have a lot of crud in the bowls. But you may get the upper passeges clear with a hundred pounds of air and some B-12 carb cleaner.

    Floats, float needles and diaphragms are critical at this stage.

    Replace the fuel line. If you want the fuel line filters get the plastic ones that you can see through. If they aren't readily available then run it with out filters.

    If the tires hold air they are good enough to ride around the block. You are not going above 30 mph, maybe. You are going to get tires in the next phase but they can wait till you get it running.

    You are going to have to check the points and the timing. You should order a set of points and a condenser but may not need them to start the bike. Look at the points in place now. If they transfer of metal from one tip to the other is very much then go ahead and replace them. I would know what this is but it is hard to describe. If unsure, replace the points.

    Set the valves.

    You will want a new pair of spark plugs. Again use them if the ones there are in question.

    Get a new air filter. Replace that. It's hard to see the dirt in an airhead filter.

    Change the oils, all the oils and the filters. I even want you to change the fork oil but if you put that one off it's OK.

    I have really bad news for you. I would have had this bike running in two days, three at the max.
    #33
  14. tete

    tete clown shoes

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    Is there a way to check if the starter is bad?
    #34
  15. disston

    disston ShadeTreeExpert

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    Starter load testing is a little beyond the ability of most home garage mechanics. If the starter is out you can hook it up and watch it spin. An indication it is good and the amount of "kick" might give you some bit of confidence but the real test is a fresh battery and see how it cranks.

    With the plugs out of the bike, make sure the plug wires are grounded. A good starter should spin up pretty fast.
    #35
  16. tete

    tete clown shoes

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    A few things I have picked up.

    Carb rebuild kit,
    Spark plugs,
    oilfilter
    drain plug crush washer
    oil filter gasket
    fuel line,
    fuel filter
    petcock washers
    clamps
    spark plugs

    tomorrow I'll pick up a battery

    BMW OEM want like 140$ or something. any lesser cost recommends that I can find locally at an parts store?

    At 140$ couldn't I just find a gel or optima battery and be done with it all?

    This week end I plan on knocking this stuff out and hopefully starting her up. at worse find out what the electrical issue might be.

    Tank is in excellent condition with NO RUST. My plan is to clean it as good as possible and let it air dry. re-install petcocks. rebuild carbs, install new fuel lines/ filters, clean air filter, new plugs, oil and filter. Im sure im still forgetting few things. whatever the case, you get the idea.
    #36
  17. Biebs

    Biebs BMW Airhead

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    Batteries Plus - in AZ:deal

    Odessey PC680 battery - takes 1/2 the space as stock fits very easy. Seat cover available on Ebay $59 made to fit stock seat.


    I had the PC680 in my 74 R75/6 4years + never charge works great fits without messing with the subframe terminals match up.

    Also check mottard-eletric new wires for battery+ and _ plus the beacon 1 LED brake light kit. All money welll spent.


    http://www.motoelekt.com/lighting.htm
    #37
  18. disston

    disston ShadeTreeExpert

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    Nice list of parts.

    Here's the battery to get. Small so you have to shim it but that's not a big deal. It's an AGM, sealed, and they are Lead Acid so they don't die all of a sudden like some other new technologies.

    http://www.batteryplex.com/toyo.cfm/m/6FM18
    #38
  19. Biebs

    Biebs BMW Airhead

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    Battery $44.95 good deal but reccommended charger $109 so $150 plus you will need a new battery in 2 years.

    Odessey PC680 Get it!!!!!!!:freaky:clap
    #39
  20. wirewrkr

    wirewrkr the thread-killer

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    What, are you a dealer for Odyssey or something?
    You can use a battery tender, and it lasts Waaaay longer than 2 years.
    Get some more experience under your belt before making a silly statement like that.
    #40