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Thread: Ludicrous idea time

              
   
   
  1. #21
    Junior Member ChazFisher's Avatar
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    Quote Originally Posted by Spaceweasel View Post
    Transmission (2004 k1200GT)
    1st gear: 2.05
    2nd gear: 1.60
    3rd gear: 1.27
    4th gear: 1.04
    5th gear: 0.90
    6th gear: 0.82

    Final drive (2006 K1200S) 2.82

    This should give me choices from 5.78:1 to 2.31:1.
    Curious why you'd go with two different gen BMWs for swingarm and transmission. That trans is made for a right-side swingarm, while the '06 is a left side. (I rode an '02 K1200RS up until I traded it in a month ago.) For that generation transmission, the flywheel/clutch slides over splines on the engine output shaft, and is bolted in place with one bolt right down the center. There's a complete parts fiche online at realoem.com if you haven't found it yet.

    I'm watching with interest!

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  3. #22
    Senior Member Spaceweasel's Avatar
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    Good eye. I wanted to use the Hossack front end of the 06 and up k12. Those have a swingarm that pivots in the frame, but the transmission is part of the engine block. As I was contemplating this I realized the earlier k bikes used a separate trans. But you are right - that requires flipping the 04 trans over to meet the left side shaft. If this prove problematic, my next theory is to try and mate a r1100gs trans into the frame. Those had the swingarm pivoting in the transmission casing itself. This would keep the trans in the appropriate orientation, and maybe allow for more spacing with my (obscenely long) motor, but I would have to move the shock mount to the other side of the frame along with figuring out how to mount the trans in the frame.

    Choosing the solution becomes something of a chicken and egg problem. I'm trying to figure out which way to go before I try and solve the engine mounts.

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  5. #23
    Junior Member ChazFisher's Avatar
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    I'd be a little leary of flipping the trans over. Pretty sure there's a breather on top, that oil will leak out. The R1100 trans sounds like a better option. I have an R1100RS transmission if you need it.

    I'm toying with using an old BMW airhead for my first electric build. The idea of keeping the transmission and avoiding some of the low-speed torque vs. top end tradeoff. So I'm really interested in how your build progresses!

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  7. #24
    Senior Member Spaceweasel's Avatar
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    I discovered the breather tube the hard way - or at least the messy way! My thought was to weld a plug into the breather to function as a drain, and to place a new breather pug in what was the drain, which would now be on top.

    The bellhousing for the 04 k12 trans looks like it was made for a 9 inch electric motor. It is such a clean connection. It doesn't look like it will connect to an RS trans, though. Oh well, such is the price of progress.

    Can you tell me how wide the RS transmission is at the pivots?

  8. #25
    Junior Member ChazFisher's Avatar
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    Quote Originally Posted by Spaceweasel View Post
    I discovered the breather tube the hard way - or at least the messy way! My thought was to weld a plug into the breather to function as a drain, and to place a new breather pug in what was the drain, which would now be on top.

    The bellhousing for the 04 k12 trans looks like it was made for a 9 inch electric motor. It is such a clean connection. It doesn't look like it will connect to an RS trans, though. Oh well, such is the price of progress.

    Can you tell me how wide the RS transmission is at the pivots?
    It's 31 cm across. 1.5cm of that are the bosses on the left side that the left footpeg bolted to, so they could be trimmed. But I realized as I measured it that its for a right side swingarm, too. So it will have the same breather tube problem. I think the only BMWs with a separate transmission AND the left side swingarm are the 2006 and up K-bikes.
    Last edited by ChazFisher; 24 August 2017 at 1822. Reason: Wrong units: cm not mm!

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  10. #26
    Senior Member Spaceweasel's Avatar
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    I was assuming that using an RS trans would involve sourcing an RS swingarm/final drive/wheel. There are tradeoffs both ways.

    R1100RS Trans/swingarm
    Pros: Swingarm pivots in trans, so i don't need to figure out how to mount the swingarm. Trans would run right side up. Possible length benefits if I can mount the transmission further back in the frame.
    Cons: Matching older rear wheel to newer front wheel might be difficult. Will need to re-weld shock mount. Cost of acquiring the parts.
    TDB: How to match RS trans to Warp9 motor.

    04 K12 trans/ 06 k12 swingarm
    Pros: Swingarm pivots in frame, so mounting is secure. Already have the swingarm and final drive.
    Cons: Trans runs upside-down, which may impact its functionality/durability. Will have to re-weld drain/breather. Possible length issues with Warp 9.
    TBD: How to mate different universal joints to match 04 to 06.
    Last edited by Spaceweasel; 25 August 2017 at 1658.

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  12. #27
    Junior Member ChazFisher's Avatar
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    Quote Originally Posted by Spaceweasel View Post
    I was assuming that using an RS trans would involve sourcing an RS swingarm/final drive/wheel. There are tradeoffs both ways.

    R1100RS Trans/swingarm
    Pros: Swingarm pivots in trans, so i don't need to figure out how to mount the swingarm. Trans would run right side up. Possible length benefits if I can mount the transmission further back in the frame.
    Cons: Matching older rear wheel to newer front wheel might be difficult. Will need to re-weld shock mount. Cost of acquiring the parts.
    TDB: How to match RS trans to Warp9 motor.

    04 K12 trans/ 06 k12 swingarm
    Pros: Swingarm pivots in frame, so mounting is secure. Already have the swingarm and final drive.
    Cons: Trans runs upside-down, which may impact its functionality/durability. Will have to re-weld drain/breather. Possible length issues with Warp 9.
    TBD: How to mate different universal joints to match 04 to 06.
    OK, I understand now. I don't think you're going to find a rear wheel for the R11xx that will match the '06 K12 front. More likely that you'll have to use two older wheels if you want them to match. My R1100RS trans has about 85k miles since a full rebuild by one of the BMW gurus. It's from a bike that was totalled because the 'ears' on the engine case that mounted the front subframe were cracked in a collision. If you decide to go that way, it's yours for just the cost of shipping.

  13. #28
    Junior Member ChazFisher's Avatar
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    I'll throw out two more ideas, probably even more ludicrous:
    1. Flip the '06 K12 swingarm. That means you'll have to figure out where to mount the paralever strut that holds the orientation of the final drive, but all the earlier K and R bikes had that on the bottom. That lets you use the '04 K12 transmission as-is.
    2. Substitute a recent vintage R12 swingarm and FD. It goes on the right side, and Realoem.com shows the pivot bearings are the same. The K12 wheel may fit, and if it doesn't the '11-'14 R1200R wheels are very similar. Don't know about the width, but I can measure my wife's '13 R1200R in the garage if you want.

  14. #29
    Senior Member Spaceweasel's Avatar
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    I like how you are thinking!

    In examining the k12 swingarm, I think inverting it runs into issues. Unlike on the R swingarms, the FD is hinged at the bottom and wants to fall open without the paralever. With a wheel attached, the pressure of the bike is trying to close it. If inverted, the weight of the bike would be acting to open it up - I don't want to trust the paralever that much.

    Also, inverting the swingarm makes it turn the opposite direction to move the wheel forward. While the Warp 9 can be run in either direction (go electric motors!) This would mean running the transmission backwards...which might work, but might not. Come to think of it, the same thing happens when you invert the transmission. instead of the swingarm, which means this would be a problem for my current set up.

    I think the cleanest solution might be using your RS transmission and sourcing an appropriate swingarm and FD. On the plus side, I might be able to use spoked wheels (if I can find a front wheel that will fit the Hossack front end) which would avoid the issue of matching wheel designs. I'll PM you to make arrangements. Thanks!

  15. #30
    Junior Member ChazFisher's Avatar
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    If you haven't found it already, Realoem.com is a complete parts fiche for all BMW cars and motorcycles. You can crossreference a part to see all the models it was used on.

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