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Thread: Difference between 81-84 R100RS and an 89 model year

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  1. #1
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    Difference between 81-84 R100RS and an 89 model year

    I am new to this to an extent. I think they changed to a mono lever rear suspension and the side cover is different. Any other notable differences between an early 80's and late 80's R100? There is a 1981 R100RS that has caught my eye

    http://www.ebay.com/itm/81-BMW-R100R...vip=true&rt=nc

    as well as a 1989 R100RT

    http://www.cycletrader.com/listing/1...0-RT-112833442

    Any education is welcome. I understand the difference between an RS and an RT. Well, maybe not completely.

  2. #2
    Administrator 20774's Avatar
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    Well, at least the '89 has the valve covers on right!

    I think you have the major differences...there are probably some other styling changes. One thing will be that the pre '85 model will have the circlip installed inside the transmission, generally thought of as a good thing. Around '85 until just before the final year of production, the circlip was eliminated, and thought to result in internal gear issues. The issues don't show up immediately but tend to over time.

    For specifications, compare the numbers from these pages:

    - '81-84 RT bikes: http://www.bmbikes.co.uk/specpages/R100RT.htm

    - '89 RT bikes: http://www.bmbikes.co.uk/specpages/R100RTmono.htm
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    Thank you.

  4. #4
    Registered User lkchris's Avatar
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    VERY major differences

    The main frames are different, as is the rear subframe. Saddlebag mounts are not interchangeable. Neither are seats. Much improved centerstand on newer bike.

    Newer bike has K-bike forks and front brakes. Newer bike has drum rear brake instead of disc. This is better.

    Newer bike has 32mm carbs as opposed to 40mm and smaller valves to match. This is also good, as the earlier valves were so big as to weaken the heads. Newer bike has 8.5 as opposed to 8.2 compression. Different exhaust systems. Exhaust valve recession problem solved on newer bike.

    Newer bike has almost nothing of the electrical system inside the headlight. It will have single as opposed to dual coils.

    Newer bike has wheels approved for tubeless tires, which older bike does not. Front wheel on newer bike is smaller diameter.

    Newer bike is approved for use with top box, which older bike isn't.

    Newer engine is likely to have folded over edge to filter canister, meaning you don't use the metal protective washer.

    Newer bike will not have oil cooler which older bike will.
    Last edited by lkchris; 08-18-2014 at 02:33 AM.
    Kent Christensen
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    ABC,AMA(LIFE),MOA,RA,IBMW MANICMECHANIC's Avatar
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    Also the newer bike will have more anti-smog plumbing under the starter cover.
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    Registered User toooldtocare's Avatar
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    And I'm not sure of this bike (the RT), but it may have the oil cooler. My 95RT had one, and so did my 88 R100RS. Everything else Kent said is right. That said, I love RS bikes, and if I were looking, I would chose it simply because it is an RS.

  7. #7
    Registered User lkchris's Avatar
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    Quote Originally Posted by MANICMECHANIC View Post
    Also the newer bike will have more anti-smog plumbing under the starter cover.
    More plumbing for sure ... for fuel vapor recovery.

    I might have mentioned in my note above that due to the electrical system change the newer bike has less fuel capacity.

    And maybe they did continue with oil coolers. With the change to smaller valves and 30-degree valve seats they really didn't need to.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

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