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Thread: 76 R90/6 - progressive suspension question and oil choice

  1. #1

    76 R90/6 - progressive suspension question and oil choice

    found someone locally who has brand new rear progressive suspension P/N 12-1203B for sale. is that the right choice for a 76 R90/6? a couple of websites say it's right for a R90S or just "R90" but then a couple of websites say otherwise, something about series 412. they're 13.5" eye to eye shocks.

    also it's about time for me to do my first oil change in this bike. what should i use? thanks y'all.

  2. #2
    Liaison 20774's Avatar
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    As for oil, there's a recent discussion of oil here:

    https://forums.bmwmoa.org/showthread...r65-proper-oil

    From some quick looking I did, it suggests they're not right for the basic /6. Seems strange...if the eye-to-eye length is right and there's enough adjustment range in the shock, it should be OK. If it was good enough for the R90S, should be OK for the R90/6.

    Of course there are plenty of alternatives. Ikon (rebranded Koni) makes a nice shock. Tom Cutter and Ted Porter offer shocks that can be built to suit your specific bike, riding style, and touring loads on the bike.
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    Registered User k12lts's Avatar
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    According to the Max BMW parts fiche, the R90/6 and R90S part numbers for the rear shocks are the same for both bikes.

    The oil question will get you several responses. My longtime German BMW mechanic says conventional 20-50 motorcycle oil in any airhead.
    2015 R1200RT, 2011 Ural Patrol, 1981 R100, 1975 R90S

    BMW MOA 37304

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    B Reams brook.reams's Avatar
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    Quote Originally Posted by k12lts View Post
    According to the Max BMW parts fiche, the R90/6 and R90S part numbers for the rear shocks are the same for both bikes.

    The oil question will get you several responses. My longtime German BMW mechanic says conventional 20-50 motorcycle oil in any airhead.
    That said, high ZDDP (aka Zinc) is a critical oil component for these bikes. Many "conventional" 20-50 oils do not have this at sufficient quantities to protect the valve train.

    Read this for recommended oils that protect airhead engines. --> https://bmwmotorcycletech.info/oilcansimple.htm

    I hope that helps.

    Best.
    Brook Reams.
    Brook Reams - Arvada, CO
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    Registered User tanker4me's Avatar
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    Methinks conventional as used in k12lts post means dino oil, and most 20-50 "conventional" and synthetic motorcycle oil includes a zinc component.
    This is an oil thread darn it!
    While synthetics now have modifiers that allow use with older type seals, I still use dino oil in the engine/transmission/final drive on Airheads.
    Bill
    Last edited by tanker4me; 10-23-2019 at 05:22 AM.
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  6. #6
    Registered User k12lts's Avatar
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    Quote Originally Posted by brook.reams View Post
    That said, high ZDDP (aka Zinc) is a critical oil component for these bikes. Many "conventional" 20-50 oils do not have this at sufficient quantities to protect the valve train.

    Read this for recommended oils that protect airhead engines. --> https://bmwmotorcycletech.info/oilcansimple.htm

    I hope that helps.

    Best.
    Brook Reams.
    I agree on the Zinc, that's why I specified "motorcycle" oil. Conventional means non-synthetic.
    2015 R1200RT, 2011 Ural Patrol, 1981 R100, 1975 R90S

    BMW MOA 37304

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