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Thread: 1974 r90/6 resurrection.

  1. #1
    Rally Rat
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    1974 r90/6 resurrection.

    So, I finally have the r90/6 home, and am gleefully taking it apart.

    I note that all the fuel lines need replacing, and that the starter button doesn't.

    Also, it's got the really weird switches on it.

    And an aftermarket front brake master cyclinder, with no connector for the front brake light switch.

    but my first concern is doping out the starter.

    The battery holds a charge, and everything else lights, turn signals, neutral switch, all work. but when I push in the right hand button, nothing happens. Am I doing something wrong?

  2. #2
    Administrator 20774's Avatar
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    Starter relay??
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Rally Rat
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    other that swapping the relay, is there a test for that?

  4. #4
    Administrator 20774's Avatar
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    Yes, knowing the pinouts, you can put 12v across two terminals and read the continuity across the other two. From Haynes, it appears that 12v goes across pins 85 and 86. If working, you should see continuity on pins 30 and 87 go from open to closed.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #5
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    thanks.. I gotta go get some fuel line, the old stuff is buggered, and a nap. I'll attack in detail once I've rested.

  6. #6
    Monza Blue 1974 R90/6
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    Couple of thoughts -

    Put a volt meter on the battery and watch what happens when you press the starter button. The battery might look like it is holding a charge, but not be able to deliver under load. If it drops way down, say below 9v when you press the starter, its the batttery.

    Next is the starter relay. You can clean up all the pins and connectors. If the red wire is corroded, it will cause the symptoms you describe. A new starter relay is $10 from Motorrad Electrik, so I wouldn't mess with the relay too long if you think it is the probelm, just replace it.

    Also, on the 1974 models, the front brake light switch is a silver plunger switch that screws into the right handgrip and is covered by a rubber boot that is very difficult to get on and off without ripping. Some 1974 models have a pressure switch in the front of the under tank master cylinder, but there are no wires connected to it.

    if you can, post some pics as you work.

    Barron

  7. #7
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    lots of pics, tomorrow. I promise.

  8. #8
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    IT RUNS!

    I put in the new starter relay, and I was just going to see if it cranked over...

    So I jumper it off to a power supply, and give the starter a tickle... 'thump-thump-thump-POP~'

    "holy -Bleep-!" I sez... "it actually -fired-."

    My curiousity dangerously inflamed, I reached for the jerry can of high-test I keep for amway salesmen, jehova's witnessess, and other special occasions. I fill the tank, which was bone dry, and rust free, if somewhat aromatic with decayed gasoline.

    the lines begin to leak... "no problem!" sez I.. I whip out from fresh 7mm cloth wrapped line, and connect everything proper like, with my one exception of routing the crossover -around- the airbox ( because it gives me a foot of spare fuel line in an emergency, that's why)

    I re seat the tank, and flip the petcocks.. each side gives a squirt of clean gas, and the lines go on.

    the right side carb began leaking, but a few whacks with a hammer freed up the float, and it stopped.

    "now" I sez "let's see just what the germans made." I set the enrichener, and thumb the switch... a staccato popping fills the air as one side begins to catch intermittantly, and then the other side takes hold, and begins to fire as well.

    IT runs! Smoothly, even.

    everything's out of adjustment, and the front end is so sloppy it's terrifying, but it -runs-.

    runs, shifts, and drives.

    known problems, so far.

    1. front end needs a -full- rebuild.

    2. horns have been removed, no new horn fitted. this must be fixed.

    3. oil change, tranny change, rear end change.

    4. at some point, new pushrod rubbers, it's drooling down the sides of the block.

    5. new kickstand spring.

    6. New battery

    Oddities...

    The bike has what look like aluminum spacers at the bottoms of the cylinders. not sure what this would do, other than possibly lower compression

    there's a data plate inside the fairing in -arabic-... I have no idea what it says, but still -arabic-.. I wonder where this bike has been, and what stories it could tell...

  9. #9
    Registered User dmftoy1's Avatar
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    1974 r90/6 resurrection.

    My bike had "spacers" and base gaskets should only have 1. If they're about 1mm thick intent was to drop compression to run lower octane gas. (I'm getting rid of them on my 74 R90/6)

    Sounds like you're making great progress! Here's my baby as of last weekend.
    ImageUploadedByTapatalk1359759188.834908.jpg

  10. #10
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    nice!

  11. #11
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    OK, here's some interesting bits...


    20130202_170516.jpg

    I can't tell if it's an arabic data plate, or just a plate with arabic on it that they used to secure the plug.. thoughts?

    Also, what are those really thick shims at the bottoms of the cylinders for, lowering compression? my r90s motor doesn't have em.

    20130202_170728.jpg

  12. #12
    Registered User dmftoy1's Avatar
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    1974 r90/6 resurrection.

    Looks like some sort of accessory plug?.

    The spacers your seeing are to lower compression to use 85 octane gas. If you look at the parts fiche online at maxbmw.com you'll see them along with a brief blurb about what they are. Snobum has a good write up on his site too.

    Have a good one,
    Dave

  13. #13
    Administrator 20774's Avatar
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    I'd post a picture (maybe the one you have) of the plate with Arabic writing in the Campfire forum and ask if anyone can interpret if for you. The plate is obviously a for the electrical connections. Maybe Luftmeister or Vetter licensed the manufacturer of their equipment to specific places in the Middle East.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  14. #14
    Registered User lmo1131's Avatar
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    Maybe Luftmeister or Vetter licensed the manufacturer of their equipment to specific places in the Middle East.
    Luftmeister may have. Vetter did not license anything to any manufacturer. We did however do proprietary fairings for several of the major manufacturers (BMW, Kawasaki, and Yamaha) until 1982. From that point on the writing was pretty much on the wall with regard to the after-market fairing/saddebag industry ... they started designing/manufacturing their own factory-installed touring gear.

    That connector, btw, is nothing we ever used; VFco used Molex almost exclusively.

    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

  15. #15
    Administrator 20774's Avatar
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    And from Luftmeister

    The plugs were basically the same as the Vetter...since the Lufty was a "direct" ripoff:
    Attached Images Attached Images
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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