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Thread: 1973 R75/5 Back-to-road Project

  1. #16
    MOA #24991 Pauls1150's Avatar
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    If you like the look of the RB2 or K112, you may want to stay off of any grooved freeways...

  2. #17
    Couldn't resist and bought the Conti classics for the looks....hope the ride won't be that bad!

    Another question, are the front pegs supposed to be offset? I can see why, so the clearance to the cylinders stays the same but feels weird to me.


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    Olaf - Austin, TX MOA #200565
    Current bikes: 2012 R1200R Classic, 1973 R75/5 www.R75slash5.com, 1969 CT 70 (108 cc engine)

  3. #18
    Liaison 20774's Avatar
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    After a bit of time, you won't even notice it. Both of my twin cylinder bikes are exactly the same.
    Kurt -- Forum Liaison ---> 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!

  4. #19
    Rally Rat 1074's Avatar
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    Offset pegs

    True story. When I worked at the dealership we had a customer come back for a warranty problem. Seems the engine was built with the cylinders offset! He was really upset and wanted a new engine.
    Boxerbruce

  5. #20
    Quote Originally Posted by 1074 View Post
    True story. When I worked at the dealership we had a customer come back for a warranty problem. Seems the engine was built with the cylinders offset! He was really upset and wanted a new engine.
    That's a good one! On my R1200R they aren't offset, so that's why I thought there is a mixed set of long/short on my R75
    Olaf - Austin, TX MOA #200565
    Current bikes: 2012 R1200R Classic, 1973 R75/5 www.R75slash5.com, 1969 CT 70 (108 cc engine)

  6. #21

    BIG PROBLEM! Would appreciate your input....

    I started going through things and did the following:

    --Checked compression, both cylinders at 130, from what I read that seems to be good
    --Started on the left side, checked rocker end play, set valve clearances and re-torqued the heads, valve clearances were slightly large but all fine now.

    Now comes the fun part. The rocker arm clearance on the right exhaust valve was too large and I realized that the head bolt from the upper exhaust rocker block was loose (maybe 10 lbs or something like that). I adjusted the clearance, made sure the rocker arm still moved freely over the entire arc and when I tried to re torque the bolt, the stud was pulled out of the engine. I applied not even 15 lbs of torque and as you can see in the pic, the bolt sticks out further than the others.

    Now what to do? I think what I can try is to take the rocker blocks off, tighten two nuts agains each other on the stud and ttry to turn the stud back into the engine case, hoping to catch a thread down there. Now if that doesn't work, what are my options?

    Capture.JPG
    Olaf - Austin, TX MOA #200565
    Current bikes: 2012 R1200R Classic, 1973 R75/5 www.R75slash5.com, 1969 CT 70 (108 cc engine)

  7. #22
    Liaison 20774's Avatar
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    Probably will have to install helicoils or timeserts where the head bolts go into the engine case. Critical step to ensure that the oil feed holes on the upper studs are not occluded to prevent oil flow out to the valve area. Here's a website with some idea of what's involved:

    http://www.gunsmoke.com/motorcycling...air/index.html

    The critical thing is getting the insert exactly parallel with the original line of the head bolt. If not, even a small amount off at the engine case will result in a big difference at the rocker blocks. The drill guide is available out there...possibly Cycleworks sells one. In a pinch an old cylinder can be used to keep things aligned.
    Kurt -- Forum Liaison ---> 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!

  8. #23
    Airmarshal-IL James.A's Avatar
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    Drill and tap guide

    There is a tool shown on page 20 of the September 2017 Airmail. hpd_online.com/stud_tool.asp High Precision Devices Inc,Boulder Colorado USA

    I have a drill/tap guide that a very good friend made for me. It weighs as much as a bowling ball. Your /5 has 97mm openings for the cylinders where as my guide has a 99mm shank for later motors. Kurt is right about avoiding a blockage of oil flow on the 2 top cylinder studs. I used my guide on a 1988 R100RS that I owned at the time. It had 2 studs pulled loose.

    I think a person could use an old cylinder to make a guide. Maybe you could knock off the bottom part of the cylinder below the fins and modify that.
    1973 R75/5

  9. #24
    Liaison 20774's Avatar
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    Snowbum has a good discussion and warnings at the bottom of this page:

    http://bmwmotorcycletech.info/break-in.htm
    Kurt -- Forum Liaison ---> 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!

  10. #25
    Thanks, I had read through snowbum's page, seems like something I may not want to do myself. I still have high hopes that I can turn the stud back in and maybe find a thread or two that grab....
    Olaf - Austin, TX MOA #200565
    Current bikes: 2012 R1200R Classic, 1973 R75/5 www.R75slash5.com, 1969 CT 70 (108 cc engine)

  11. #26
    Dang, those tools are expensive! Probably makes more sense to find someone who has the tools, assuming I only have to do this once (knock on wood!).
    Olaf - Austin, TX MOA #200565
    Current bikes: 2012 R1200R Classic, 1973 R75/5 www.R75slash5.com, 1969 CT 70 (108 cc engine)

  12. #27

    What oils are you using?

    While I am still pondering what to do with my head bolt I want to tackle some easy stuff and change my oils.

    What engine oil are you using? My riding in CenTx can be in temperatures from the upper 50s to the lower 90s. I never really had any overheating problems with my R1200R, which amazed me, so hopefully it will be fairly similar with the airhead. Any brands of oil you prefer?

    As for the transmission, drive shaft and final drive, the PO gave me 3 bottles of Castrol Hypoy C SAE-80-W-90 that have been sitting on his shelf for 10 years. Two of the bottles are still sealed, would you use them or does oil "expire"?
    Olaf - Austin, TX MOA #200565
    Current bikes: 2012 R1200R Classic, 1973 R75/5 www.R75slash5.com, 1969 CT 70 (108 cc engine)

  13. #28
    Liaison 20774's Avatar
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    Olaf -

    The March 2013 Owners News has an article I did on engine oils. You should use an oil specified by the users manual with is an SG/SH rated oil in the 20w50 grade. The article will show you ratings of oils and their chemical makeup.

    As for gear oils, there will be opinions on whether to use unsealed oil or not. IMO, I would recycle those oils and just buy new GL5 80w90 gear oil. Just not worth any possible risk.
    Kurt -- Forum Liaison ---> 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. #29
    Thanks Kurt, great article!
    Olaf - Austin, TX MOA #200565
    Current bikes: 2012 R1200R Classic, 1973 R75/5 www.R75slash5.com, 1969 CT 70 (108 cc engine)

  15. #30
    Registered User
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    Quote Originally Posted by anotherbmw View Post
    Thanks, I had read through snowbum's page, seems like something I may not want to do myself. I still have high hopes that I can turn the stud back in and maybe find a thread or two that grab....
    I recommend Time-serts over Helicoils.

    And Kurt is right about getting it perfectly square during installation. I just put two in the final drive of my R90/6, it's not something I would suggest you do yourself unless you have a machining background and have the proper equipment available to use.

    20171005_121140.jpg

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