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Thread: 1973 R75/5 project.

  1. #1
    Rodney Aiken Ctrod's Avatar
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    1973 R75/5 project.

    Hi all
    IÔÇÖm going to give documenting this project a shot and hopefully anyone that starts to read it wonÔÇÖt be too disappointed.
    This is my project. Looks straight forward enough. The plate says it hasnÔÇÖt been registered since 1988. I know itÔÇÖs been park in my friends garage about that long without moving since he got hurt. It was a project bike for him back then, I donÔÇÖt think he ever had it running.
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    Rodney Aiken Ctrod's Avatar
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    The back story

    He was home when his father called and said a friend of his was getting rid of a couple of old BMWÔÇÖs for free and did he want them. Of course he said yes and the next thing he knew his father was pulling in the driveway with a trailer full of parts. I guess this one was mostly there so he took what parts he need for it and got rid of the rest. He got hurt at work and itÔÇÖs been sitting in his garage for at least 12 years.

    I mentioned to him one day that if he ever wanted to sell it let me know. He said ÔÇ£ come get it. You can have itÔÇØ I was there the next day. I didnÔÇÖt realize he didnÔÇÖt have any paper work for it so that was my first project, to make sure I could get it registered before I put any more money into it, I wonÔÇÖt go into all the details but that took about 6 months.

  3. #3
    Rodney Aiken Ctrod's Avatar
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    The gas tank

    Registration in hand I was ready to start.

    This I donÔÇÖt know if I would have started if I had know how much time I would end up putting into it.

    When I took the gas tank off it felt pretty heavy. I turned it over, over a bucket and what looked like sand came pouring out. I put a handful of nuts and bolt in it and shook it. By the time I was done I had about 6ÔÇØ of sand in the bottom of a 5-gallon pail and there was still a hard crust at the bottom of the tank that wouldnÔÇÖt loosen up. Even poking at it with a long screwdriver. I took the tank outside and ran water through it until the water looked pretty clear and than I put a little Marvel Mystery Oil in it and waited for it to warm up out side.
    Skipping ahead.
    Now that itÔÇÖs warmer outside. I started by rinsing the tank out with dish soap and a lot of water. Using the old petcocks to block the hole in the bottom of the tank IÔÇÖd put dish soap in the tank and then fill the tank with water from a hose. The soap bubbles would bring a lot of the rust particles to the top and out. Once the tank was full of water and no more rust was coming out I pull the petcocks out and let the water pour out. I did this over and over, at least 2 dozen times, until the water look clear of rust. Then I filled it a few more time to get all the soap out.
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  4. #4
    Rodney Aiken Ctrod's Avatar
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    I used Tank Cream on the inside of gas tank. And this is what I got out of the tank after I let Part A sit over night. This is just the bigger pieces I picked up off the ground. After this it was pretty straightforward. Pour in part B, roll around in the tank and pour out. Pour in part C, roll around and pour our.
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    Rodney Aiken Ctrod's Avatar
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    Tank Cream

    This is tuff to use without getting on the paint. You need to roll the tank around to make sure you cover the inside of the whole tank and some came out the filler. I did damage the paint slightly. Luckily the paint wasnÔÇÖt that great to start with.

  6. #6
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    cool. good luck.

    mods- you want to move this over to Airheads, where it belongs?
    Ride Safe, Ride Lots

  7. #7
    Rodney Aiken Ctrod's Avatar
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    Starting the carbs

    Over the winter I worked on the carbs. It came with Bing 64/32/9-10 CV Carbs. These were gunked up pretty good. I let each one sit in a gallon of parts cleaner overnight before I tried to take them apart. The first one came apart relatively easy. The second one not so much. No mater what I tried I couldn’t get the float pin out and than I snapped off the top of one of the jets. Most of what I’d read about the 64/32/9-10 carbs was pretty negative so I decided to see if I could find newer carbs on E-bay. I read that the newer ones work better. I found a pair of 64/32/19-20 online for $165 and I bought the DVD and book from Bing. The DVD was good and gave me a lot more confidence in what I was doing and the book gave all the jet sizes and other info for all the different years and carbs. The book is also interesting because there is a lot of detail on how the carburetors work.
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    Last edited by Ctrod; 06-13-2012 at 08:10 PM.

  8. #8
    Administrator 20774's Avatar
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    Not sure if you realized that the float pins are knurled and they only come out one direction. Too much pressure and it's possible to break off the bosses that hold the floats in...that will pretty much ruin a carb. And soaking as in complete dunking of a carb in solvent will also probably destroy the o-rings that are on the butterfly shaft. But if you're replacing them anyway, I guess that's not a problem. As the DVD will tell you, the butterfly plates are attached to the shaft and the screws are peened in place so they don't back out. This needs to be defeated or reveresed in order to successfully remove the shafts.

    I was reading something the other day by Tom Cutter...if he ever receives a carb in which the screws has been loctited into place, he just cuts off the shafts and replaces new. A) it can be more difficult to remove something that has been loctited. B) he doesn't have time to waste doing that.
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    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  9. #9
    Registered User lmo1131's Avatar
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    he just cuts off the shafts and replaces new.
    That's tight quarters, he must cut through the shaft and the butterfly. A handheld 32T hacksaw blade and yer done in three minutes.

    $9.98 for the shaft, and $4.91 for the butterfly! Whooda thunk it; cheap BMW parts!

    Whatever his shop rate is, he couldn't possibly fight through it for $15.
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

  10. #10
    Rodney Aiken Ctrod's Avatar
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    The projects on hold for a while.
    I mounted the carbs and kicked is over untill I was blue in the face but got no love. It's has spark and fuel but it just won't even give a pop like it wants to start.
    I think I went as far as I can without sending more money on it' and thats been put on hold till the bank account builds back up. I just sent 3K on my work truck and was just told my car needs about 1k of work so the bike is pushed back into the basement for a while. It's been sitting for over 12 years and now I guess it will have to wait a little longer.
    Pretty disapointing, I was really hoping to take it down the Blue Ridge next summer.

  11. #11
    Monza Blue 1974 R90/6
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    When you say "kicked it over" do you really mean kicked with the kick starter? I think the bike has to be pretty well tuned to start with the kick starter, so it wouldn't surprise me if yours didn't start.

    What left to spend money on to get it running? If the valves are set right, you have the carbs done, all that is left if making sure it has spark and is timed right.

    Barron

  12. #12
    Hopelessly lost subagon's Avatar
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    Reach out to the local state chapter of the Airheads (www.airheads.org). Most hold annual tech days and the old gurus will be happy to help/teach you get it running.
    Mike Barfield - Plant City, FL
    '07 R1200 GS - '75 R90/6 - '93 R100GS PD - '71 R60/5 - 2 X '73 R75/5 LWB - '83 R80 ST
    Picts

  13. #13
    beemerfield
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    Keep going! If you have a decent battery, you should be able to at least have it running. Maybe you get to ride it a bit and figure out what you need to work on over the winter.
    beemerfield

  14. #14
    Registered User lmo1131's Avatar
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    Yeah, don't stop now! You're within the realm of "free" stuff to get running.

    If you have a decent battery, you should be able to at least have it running.
    Points gapped @ .016" (don't forget to lube the cam block (very sparingly)).
    Plugs gapped @ .024-.026"
    Ignition timing set: somewhere close (static method)
    Valves set: Ex .008", In .006"

    Carburetors rebuilt: Did you have the butterfly out? Did you get them back in correctly? (read > http://bmwmotorcycletech.info/earlybingR75CV.htm)
    Fuel to carburetor bowl: check
    Float height: ((parallel with the bottom surface of the carburetor/float bowl when the needle valve seats) float bowl fuel level affects the idle circuit))
    Idle mixture needle valve: 3/4 turn back from "closed" (this is a guideline but should get you started).
    Idle speed screw:set

    Throttle cables: set (with 1/16" +/- free play (slack))
    Choke cables: set

    Battery fully charged:
    Oil level: check

    Fuel, Air, Spark.... it should start.

    Excellent photo documentation of the Bing 32mm > http://www.pt-photos.com/carb_page.htm
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

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