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Thread: 1977 R100: rear brake hub-cam stuck

  1. #1
    Registered User kwb210's Avatar
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    1977 R100: rear brake hub-cam stuck

    The bike: 1977 R100
    I just picked up this bike and for the price I did not take to close a look at much more than the Vin# on the frame and title, making sure they matched.
    The rear brake have the cam that passes through the final drive housing and I have never had an issue with one not wanting to move. Frozen! I have just began some Kroil penetrating oil on both the inside and outside. My question is: is the cam piece screwed on or pressed on to the shaft?
    Here is the shaft number I am speaking of: 35 21 1 230 261 REAR BRAKE CAM (to 09/80), (courtesy of Max BMW) and here is the picture just in case I did not describe the piece well. With a 12 inch adjustable wrench you can barely turn the shaft.
    I just finished a topend reseal and general cleaning of the bike, very very greasy/oily mess. I pulled off the oil pan just to see what may be living in there, and I lucked out, barely a discolored coat of oil, not black as I expected, so, I am assuming maybe the guy actually changed the oil on a regular basis but cared less about the oil dripping out of the push rod tubes, dripping is being nice!
    Thanks!!
    Kurt
    Attached Images Attached Images
    1977 R100/7 1971.1972.1972.1973 R75/5
    1974 R90/6 multiple boxes
    Airhead Revival
    "Objects in the mirror appear to be losing" unk

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    Can't remember how it's attached (I'll have to look) but on my R60/6, once you remove it, there are indentations in the shaft portion behind the cam which is to hold grease. You're supposed to grease that at intervals. Last time I did mine was about 20 years ago, so it lasts a while.

  3. #3
    Registered User kwb210's Avatar
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    just found this picture

    As I was reading a build project I came across this picture. Now I believe I just have two figure out how to remove the cam. It looks like I can maybe push or press it out, pressing from the outside cover. Any additional comments would be great!
    Attached Images Attached Images
    1977 R100/7 1971.1972.1972.1973 R75/5
    1974 R90/6 multiple boxes
    Airhead Revival
    "Objects in the mirror appear to be losing" unk

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    That brings back memories...I believe you just remove the lever that attaches to the brake rod on the driveshaft side and it will just push through (or pull from the other side). Mine is not pressed in. See those grooves? Put some grease there after you have polished it up a bit with some emory cloth.

  5. #5
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    Try using PB Blaster ( or similarly called - available most everywhere) on the shaft. Then use some heat on the outside part, and try to keep the shaft as cool as possible. Aluminum expands faster than steel, and sometimes in conjunction with the Blaster, often loosens it up enough to get it to start turning.

    Worked very well on my son's VW Golf windshield wiper shaft and housing. Almost an exact duplicate situation, materials, etc.

    Be careful to NOT localize the heat in just one small spot, try to spread it around - just keep off the shaft. Also, putting ice on the shaft where you can will "shrink" it.

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    Patience pays dividends

    Heat may be a good thing but unless you have a good knowledge of where, how long and how hot you can go you should just stick to the PB Blaster a little patience and the 12" crescent wrench. Those groves in there are for grease and if you heat that up a little to much you have boiling grease and if there's moisture (water) trapped in that grease (which expands really quick) it might go poof splat and make your day a bad one. If you use heat use a heat gun set on low and heat the hole F/D slowly after you have drained the gear oil and left the fill and drain plug on the bench and only heat it enough to get the cam to turn a half turn or so and then work on it from there. It should come out with a little twisting and hand pressure after you get it moving and well lubed with PB Blaster. Yes I but it by the drum cause it works.

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    Quote Originally Posted by 69ZEFF65 View Post
    Heat may be a good thing but unless you have a good knowledge of where, how long and how hot you can go you should just stick to the PB Blaster a little patience and the 12" crescent wrench. Those groves in there are for grease and if you heat that up a little to much you have boiling grease and if there's moisture (water) trapped in that grease (which expands really quick) it might go poof splat and make your day a bad one. If you use heat use a heat gun set on low and heat the hole F/D slowly after you have drained the gear oil and left the fill and drain plug on the bench and only heat it enough to get the cam to turn a half turn or so and then work on it from there. It should come out with a little twisting and hand pressure after you get it moving and well lubed with PB Blaster. Yes I but it by the drum cause it works.
    The purpose of the heat is to expand the aluminum housing - as long as you don't centralize the heat on one location there is almost nothing that can go wrong.
    don't be alarmed.

  8. #8
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    Reference mark

    It helps with correct reassembly if you take a small,sharp chisel and punch a reference mark on the shaft where the slotted pinch point is on the arm prior to removal.I would suspect that the brake lever could use a lube too.Just a few more minutes and the action will be smooth as butter!
    Russ

    '76 R90/6 '78 R80/7 '78 R100RS big pipe

  9. #9
    Registered User kwb210's Avatar
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    Got it!!!

    Thanks for all the helpful comments, a little bit of each one and task completed! I continued use of Kroil penetrating oil, then choose a heat gun rather than a torch (torch is way more fun but not needed here) the heat gun allowed me to concentrate the heat on the bigger rather than the smaller metal areas. A couple of light wacks with a hammer and piece of wood to protect the arm, it slid out. Simply a case of VERY dried up grease and probably years of no movement. All cleaned up and a bit of grease, slid back in and the rear brakes are back in the business of braking! Thanks! Of all the bikes I have worked on I had never come across a brake cam that was so stuck.
    Kurt
    Attached Images Attached Images
    1977 R100/7 1971.1972.1972.1973 R75/5
    1974 R90/6 multiple boxes
    Airhead Revival
    "Objects in the mirror appear to be losing" unk

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    Great news

    Thanks for the update!!!

  11. #11
    Alps Adventurer GlobalRider's Avatar
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    Quote Originally Posted by kwb210 View Post
    My question is: is the cam piece screwed on or pressed on to the shaft?
    Even though you got it out...for the next owner...

    Neither; it is machined as one piece. It slides right into the rear wheel drive.

    Spray both ends of the brake shaft with PB Blaster or the Kroil that you have. Use a plastic faced hammer and tap both ends of the part while applying the force to the brake pedal.

    Don't give up. It took me some 4 hours to get a bolt out of a clearance hole in an aluminum casting without damage.

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