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Thread: Final Drive

  1. #1
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    Final Drive

    Have a 1978 R100S with an after market rear disc brake. The plug where the original drum brake entered the final drive plate popped out. How do I fix? Has this interfered at all with the final drive fluid?

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    Final Drive

    Where the drum brake lever entered the final drive plate. Sorry

  3. #3
    Registered User toooldtocare's Avatar
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    See Max BMW website http://www.maxbmwmotorcycles.com/fic...7&rnd=04302013

    I believe #13 is what you are looking for.
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    Popped out???

    Its a threaded plug type screw to the best of my knowledge so it shouldn't pop out. The brake activating shaft hole should have a plastic plug stuck in from the outside and it could pop out and get lost.

    Was it in the pivot pin hole which is threaded or the brake activating shaft hole which is through and through without threads?

    Did it bounce around inside your F/D and wheel hub when it popped out? That may have caused some issues if it did.

    Its a good idea to keep both holes covered and sealed up good to keep dirt and stuff out of them so it doesn't build up and make a mess but you shouldn't leak fluid if they are not in place.

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    Not a threaded hole.

    Not a threaded hole. So I guess all I need do is plug it. Now it seems I need a new seal on the filler plug to the f/d oil filler. Must be what leaked all over the rear wheel.
    Last Import - 1.jpg (Well, that's supposed to be a photo.)

  6. #6
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    Looks like someone pookied a plug to that hole...I'm not sure that's the proper way to seal that. The filler plug is the hex plug right next to this hole. The oil level in the drive should be not very far below that open hole. It really needs to be plugged. I don't recall...does the brake rod that normally goes through there run though an internal cavity? If not, I wonder with is plugging the internal opening to the brakes?

    It's hard to tell where the oil seepage is coming from...it could be from that small hole just below the axle nut...this drains off any oil seepage past seals in the final drive. Or it could be from the vent at the top of the drive. Rare to see oil coming from there...although we did have a thread recently on a later model final drive that was missing a baffle, thus allowing some of the oil to make it to the top vent/filler.
    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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    Think I've got it figured. Hole is from the old drum brake cam shaft, through and through and needs a better plugging. Oil leek from weep hole means I've got to find what inner seals need replacing. Thank you all for the replies. Anybody know where I can get a manual more specific to this bike? The Clymer r50/5 through r100gs 1970-1996 is too confusing for me.

  8. #8
    Registered User lmo1131's Avatar
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    edit - Haha... your post beat me by a few minutes..

    In new(er) condition the plug looks like this. The one you have has had the top broken somehow. Go to an Ace hardware store and find an appropriately sized "hole plug" to install; the BMW p/n is 33 11 1 236 826 and lists for $.59 from MAX.



    There shouldn't be, any oil coming from this bore (it's simply the vestigial bore for the brake cam); if there is you have more serious problem, like a cracked FD housing, or oil getting past the gasket ("#2) under the inner housing cover (#1). Judging by the oil slung all over your rims, and what looks like seepage from the overflow hole under the axle nut a blown gasket might in fact be what's going on. If you remove the rear wheel it should become readily apparent if it has.

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

    Lew Morris
    1973 R75/5 - original owner

  9. #9
    Registered User lkchris's Avatar
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    My 1978 R100S came with a rear disc brake from the factory. Of course it had snowflakes.

    In any event, I'd think it doubtful there was ever an "aftermarket" rear disc brake, save of course for the rotor itself. Maybe somebody cobbled on a Honda part or something, but it seems more likely you have BMW parts.

    You'll fix what you have with advice above, but the best advice is to convert to rear drum brake, as the Airhead rear disc brake was and always will be more trouble than it's worth.
    Kent Christensen
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    '12 R1200RT, '02 R1100S, '84 R80G/S

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    Heat damage

    It almost looks as though the plastic plug got overheated and started to melt, that could also explain the oil coming out of the vent hole. I would have the F/D checked for bad bearings or improper shimming just to be on the safe side and if the bike is relatively new to you.

    Gremeca had an aftermarket rear disc set up for earlier airheads. I picked up an R 90S with one and a set of Morris mags.

  11. #11
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    Thanks, you guys. Looks like I'm pulling the rear wheel.

  12. #12
    Registered User kwb210's Avatar
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    R90S w. disc on Morris wheels

    I picked up a very late 1976 R90S and it has a rear disc mounted on Morris wheels. The seller had it in his living room (generally considered a good sign, or he was single and had no garage), he was the second owner and did not know the details of the disc installation. Is it possible a dealer may have made this change? Morris wheels are not common, Lesters were common. I sure would appreciate any comments on the 90S w a rear disc. I purchased it and have not even ridden it! It had sat for many years and until I have the time to properly review it's condition I will just let it sit. Lucky for me the guy had drained all the fuel out when he wheeled it into his home. I guess we would all do that...actually, as soon as my wife got home it would be wheeled right back outside!
    Regards,
    Kurt

    PS: I should probably update my sig line...I get kind of funny with slash 5's so forget about the others.

    Quote Originally Posted by lkchris View Post
    My 1978 R100S came with a rear disc brake from the factory. Of course it had snowflakes.

    In any event, I'd think it doubtful there was ever an "aftermarket" rear disc brake, save of course for the rotor itself. Maybe somebody cobbled on a Honda part or something, but it seems more likely you have BMW parts.

    You'll fix what you have with advice above, but the best advice is to convert to rear drum brake, as the Airhead rear disc brake was and always will be more trouble than it's worth.
    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

  13. #13
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    Mine was a mid 75 R 90S

    My R 90S with disc and Morris mags is a mid 1975. Just a slight detour to offer a solution please. If you want to keep the bike in the living room just buy her a bike that she likes and put that in there along with the R 90S. I've had my R69S and his and her W650's in the living room for several years now.

    I think the Gremeca rear disc and Morris mags were an aftermarket set up kit. Mine has a stainless brake line and all the brackets and mounts look to be very well made. I'm hoping to find a Nissan caliper and master cylinder to fit so I can put the stuff and the mags to use on a project bike.

    I do recall seeing a Smoke Silver R 90S at the Johnson City national that had an after market rear disc and spoked wheels. The bike had a number of very nice period correct upgrades like large oil pan and Hella spot lights. Unfortunately I didn't pay attention to the details of the rear brakes.

  14. #14
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    Quote Originally Posted by 69ZEFF65 View Post
    I do recall seeing a Smoke Silver R 90S at the Johnson City national that had an after market rear disc and spoked wheels. The bike had a number of very nice period correct upgrades like large oil pan and Hella spot lights. Unfortunately I didn't pay attention to the details of the rear brakes.
    I saw that very same bike there too. I talked to the owner and he was more of a typical Airhead owner who bask in the glory of doing everything themselves on their bikes better than any dealer can do. He said he did the conversion all by himself from scratch and didn't want to reveil much detail as far as the individual components.

  15. #15
    Administrator 20774's Avatar
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    Quote Originally Posted by EMSimon View Post
    he was more of a typical Airhead owner who bask in the glory
    We "bask"? I didn't know that...some kind of aura or something??
    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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