How many different double-sided Airhead swingarms are there?

Discussion in 'Airheads' started by Milagro, Nov 29, 2008.

  1. Milagro

    Milagro Been here awhile

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    Hi All,

    I have an R75/6 that I had hoped to upgrade to the cush driveshaft (all metal with spring assembly, typically found on '79-'80 bikes). I bought a used cush shaft and yet the diameter of the splined section on the shaft itself is still too large to fit through the necked-down portion of the swingarm. :bluduh

    Now I know that there was a swingarm for the SWB R75, a longer version for the LWB R75 and a swingarm developed for the newer Airheads that used a driveshaft that incorporated a rubber damper assembly. It also seems like there must have been a swingarm for this cush shaft design as well.

    From the fiche pics, it looks like the swingarm that I would need in order to use the cush shaft would have no "necked-down" section on the swingarm, allowing the larger diameter splines to be fitted in the arm prior to attaching the spring, splined cup and attaching hardware.

    Does this sound correct? Were there a total of four double-sided swingarms manufactured, with one additional model being only used on the R75 SWB?

    Thanks,

    M
    #1
  2. jtwind

    jtwind Wisconsin Airhead

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    On the 79-80 cush drive shafts the threaded part of the driveshaft has flats machined on opposite sides that allow it to be fed through the narrower swingarm. You could have the flats machined on your shaft to allow you to do the same. You might even be able to grind and file them on yourself. Without them you need a later than 80 swingarm. It's possible the swingarm your shaft came out of would work.
    #2
  3. Milagro

    Milagro Been here awhile

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    Done! Thanks JT. Now I have to figure out how to compress that spring far enough to install the circlip! Any special techniques that you might be able to share?

    Thanks again!

    M
    #3
  4. Hawk Medicine

    Hawk Medicine Coyote's Brother

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    When you bought the cush driveshaft, you should have bought it complete with the "Big Tube" swing arm.

    Why? Because the BT swing arm is a direct, bolt in replacement for the older SA but it's much stronger, giving you the same benefits you'd gain by having your stock part braced by San Jose BMW for much morer $$$.

    I have that BT/cush combo on my R-90SPL and its a huge improvmentover the twist-prone stocker and you can usually find em pretty cheap as used items.
    #4
  5. xavier296

    xavier296 Alaska n'Back

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    I have read different opinions on which driveshaft to use. I bought a big tube swingarm with cush drive, and was going to use the cush drive like this thread discusses, but it seems that there is a whole nother school of thought of using the solid shaft. So, whats the real word? Does the solid shaft fail? Does the cush drive take away a significant amount of power?

    Also, In have seen special tool for removing the solid shaft. Can I just use an airgun and remove the bolt on the spline side and pull it all out?
    #5
  6. boxerboy81

    boxerboy81 Stay Horizontal

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  7. xavier296

    xavier296 Alaska n'Back

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    Thank you, but that is how you remove the cush driveshafts, not the solid ones.
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  8. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Can't help much on pulling the shaft apart - but I did the conversion of installing a solid shaft in the newer swing arm. Back when I did it, the consensus was the cush made shifting easier. Since none of the bikes before 1981 had a cush drive shaft, I opted out, wanting the simplicity and less rotating/unsprung mass of the solid shaft. And I never noticed shifting being any worse - it actually shifted very nicely.

    If you enjoy jack-rabbit starts it might be a good idea to leave it in. But plan on replacing its parts every now and then when it starts slipping. Then again, if you like jack-rabbit starts, it'll probably slip on you spoiling all the fun. :lol3
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  9. xavier296

    xavier296 Alaska n'Back

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    Hmm, another knowledgable guy who has never taken a solid shaft apart. I know they sell a tool to do the job, but I don't see its need.

    I guess I just have to take the bolt out and see if it all falls apart.

    My bike rode very nicely with the solid shaft, so I would prefer the "less moving parts" approach also.
    #9
  10. wirewrkr

    wirewrkr the thread-killer

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    He knows waaay more than you, trust me.
    If you take the nut off and it just falls apart, you will need a new drive shaft and bell coupling because the taper that keeps it from spinning will be toast.
    There are special puller tools needed to do the job properly. It is a fairly complex affair and if you have a lathe and patience maybe you can make them your self.
    Some folks have tried to manage with out the tools and butchered the other parts in the process.
    #10
  11. Airhead Wrangler

    Airhead Wrangler Long timer

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    I'm putting a solid shaft in my monolever when it goes back together. I didn't like the vague springy feeling the cush shaft gave the rear end. Maybe the spring in mine had lost some of it's stiffness, but anywhere with a lot of on and off the throttle it added a little lag and awkwardness. Let off the throttle and there's a bit of a lurch before the engine started braking. On the throttle again and another lurch as it accelerated again. Mine never slipped as wirespokes mentioned though. I didn't realize that was possible.
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  12. xavier296

    xavier296 Alaska n'Back

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    Wirewrkr, in your attempt at causing strife in yet another thread, you mis interpreted my comment as saying I knew more than him about airheads. I certainly did not say that, and rather appreciated his response. My questions are usually answered quickly and simply, so it has been interesting that the solid driveshaft disassembly process seems like a mystery to many.

    Through the sarcasm and belittling, I assume from your comment that removing the bolt will do nothing, as the splined output is a press fit to the driveshaft and requires a special tool to separate. Thank you for clearing that up.
    #12
  13. Wirespokes

    Wirespokes Beemerholics Anonymous

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    xavier - I think we're having a 'miscommunication moment' here. wirewrkr wasn't causing strife as I can see, so this must be one of those difficulties dealing with the written word. It's so much easier when talking with someone face to face.

    I've never pulled one apart simply because there never was a need. Those oil-bathed shafts rarely have problems. I've taken the cush shaft apart - but forget why as it was a long time ago. But I made a tool to compress the spring to be able to pull it apart. The non-cush evidently have a taper the flange slides on and if it's anything like the trans output flange, I'm sure it'll need special tools! :lol3

    wrangler - you said it better than me - I meant the lurch like you mentioned. But when they get bad they can rotate 180 degrees (or more) before finally solidly engaging.
    #13
  14. Max Headroom

    Max Headroom lost in the '70s

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    I pulled a solid driveshaft apart a few weeks ago, and I used a bearing splitter together with a hydraulic puller set to remove the bell. This one was the tightest I've encountered, and required a lot of force to separate. The hydraulic puller is capable of up to 8 tonnes of force, and it seemed like I was at least approaching that limit.

    It came apart with no damage to the driveshaft, swingarm, bell or nut.
    #14
  15. wirewrkr

    wirewrkr the thread-killer

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    Well, I wasn't, but what the hell, I might as well now. I'm a crusty old bastard and don't care.
    Piss off.
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  16. Caddy82rats

    Caddy82rats Long timer

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    Y think also the cush drive is softer for the gear box, less stress
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  17. wirewrkr

    wirewrkr the thread-killer

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    I would tend to agree with that. I'm sure that it had something to do with BMW losing the heavy flywheel that same year.
    #17