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Thread: Hydraulic Clutch

  1. #1

    Hydraulic Clutch

    I have been trying to figure out what size the clutch cable hole on the primary is and I found 5/16 24. I was not able to definitively confirm this so far.
    My goal is to build a hydraulic clutch system. I know there are already kits out there but I prefer the DIY direction. I just like to mod my stuff.
    Trying to find the size of the bolt hole or a compatible slave cylinder for our bikes is my first step. I will drill and tap the clutch cable hole if I just can't find anything compatible.

    Any other tips you might have would be great. I appreciate all the help I can get!!

  2. #2
    Senior Member 34nineteen's Avatar
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    Just remember that the Buell/Harley mechanism requires a “pull” not a “push”. So you will need to find a pretty unique cylinder to do that, if you are trying to use the stock cable hole.

    It’s probably easier to mod the adjusting cover to use attach a mechanism to.

    I had the Magura setup on my bikes and the trick on the XB is to keep the hose away from the exhaust heat, while keeping it somewhat protected from external damage. The end result was that it was only marginally better than the stock setup after replacing the cable and lever.

    Not saying it can’t be done, but I’d recommend checking out the Sportster forums to see if anyone found a slave cylinder to work. That will be the trick. The master should be pretty straightforward.

  3. #3
    This is just a random rod on ebay but the majority of these say pull rods.
    https://www.ebay.com/itm/Hydraulic-C...0AAOSw8gVX95nf

    Other than the size of the screw thread and pitch wouldn't something like this work? It has the length in its adjustable range. It moves 11mm total.
    I did locate the Magura slave for around 100$ which may be what I do if this doesn't pan out in the end.

  4. #4
    Senior Member 34nineteen's Avatar
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    That looks like the Magura slave cylinder. Sounds like you are on the right track.

    If push comes to shove, you could always drill and retap for the needed thread size.

    Dont forget to make sure the pull is enough. I dont know the stock spec, but its probably easy enough to pull the clutch cable from the housing and measure the pull to make sure its the same.

    Keep us posted!
    Last edited by 34nineteen; 05-15-2018 at 09:46 PM.

  5. #5
    Senior Member Cooter's Avatar
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    Modding the stock cable system in that way is indeed possible, but what is your goal?

    It would be DIY unique if that what your after, but it doesn't address the clutch pull effort you need because the lever throw will have still to equal the piston pull unless you make the ramp steeper (I wouldn't) or the fingers shorter.

    OR the weak parts of the cable system it has now. You're still using the cover ramp thats known to fail and theres still a cable on end of the pull slave cylinder that can break and you are adding the weak parts of a hydraulic system to those faults as well. The 'pull' slave will be sticking out in a rather fragile fashion, Leaks, air, hose failure, seals leaking, blah blah. So you are adding lots more weak points to a very simple cable system without eliminating any.

    If you are looking for an upgrade, a way to truly 'upgrade' the stock Buell cable system to hydraulic, and actually get rid of the cable weak points would be to mod the clutch cover to accept a 'piston style slave cylinder' that would push directly on the clutch pack without (your way) having to convert hydraulic pull to cable pull to ramp pressure, to then push on the clutch pack. Using the piston style slave also drastically reduces the length of push you need (long skinny piston pull the way you're thinking vs. short fat piston push). That will allow you to tune the clutch lever effort and throw while still having enough power to press the clutch pack.

    You are in luck! The vast majority of bikes with hydraulic clutches keep the slave cylinder in the cover (FYI the Buell 1125's and EBR's do...) So theoretically all you need to do is make a hybrid cover. Get a 1125 clutch cover with the piston to bolt up to a stock XB cover, then run a hose to a stock 1125 clutch master on the bars. Sounds easy right? Heck, add a manifold vacuum hose to the 1125 clutch and voila, it's a 'slipper' clutch too! All you would have to do is tune the length of the pushrod, or engineer that into the height of your hybrid cover.

    I like that idea! Make a few while you're at it, I'll buy one

  6. #6
    Senior Member 34nineteen's Avatar
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    I wonder if a late model Sportster primary cover will fit a Buell XB engine? If thats the case, there is the Random Engineering piece that replaces the derby cover with an actuator.

    When I did my Magura conversions, the pull was only marginally easier than my existing setup. On my last XB, I just replaced the lever and the cable and got a pretty good improvement.

    Heck, I'm still trying to get Cooter to engineer me a t-shirt.



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