cr500 gets a rekluse Core EXP

Discussion in 'Some Assembly Required' started by jar944, Apr 20, 2014.

  1. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    752
    Location:
    Chantilly VA
    I installed a core exp in my YZ250 I really liked the results and wanted to add one to my cr500 to make it a better "do-all" bike. The biggest problem is that Rekluse doesn't offer a core exp for the 500. They Do however offer one for the Cr250 and Crf450. The good thing about that is the 250/450/500 share the same clutch plates and have the same transmission primary shaft dimensions. With that being the case I called up rekluse and bought some of the parts for this project just over a year ago
    [​IMG]

    The biggest hurdle (or so i thought) was the lack of a available (deeper) clutch cover from rekluse that would fit the 500. I knew I needed to fabricate one for the project to actually move forward. Unfortunately making oe took a back seat to a bunch of other things and the project just sat collecting dust.

    Fortunately that gave me time to become familiar with the principals behind its operation and better understand the requirements for it to work on a 500.

    measurements from the exp "ring":

    Total wedge weight 159g (factory heavy wedges)
    wedge spacing diameter (centers) min 124mm, max 131mm
    ramp angle 18.5 deg
    opposition spring force (not measured)

    engine parameters
    primary[​IMG] reduction 2.52:1
    idle RPM 1500 rpm



    F<sub>c</sub> = m v<sup>2</sup>/r
    = m (n 2 ? r / 60)<sup>2</sup>/r
    = 0.01097 m r n<sup>2</sup>

    where
    n = revolution per minute
    Or in this case

    .01097*m*r*(n*n)
    m = .0159kg
    r = .062m
    rpm = 595

    .01097*.0159*.062*(595*595) = 38.3N

    Which lead me to wonder how one would calculate how much torque a clutch could theoretically hold (hello unform wear theory)

    [​IMG]

    once I had that I was able to put together a spreadsheet to play around with the clutch parameters

    [​IMG]

    With that done I came to the conclusion that the factory "heavy" wedges were going to slip to much at low RPM. I needed more weight in the wedges but being somewhat limited on space the only viable method in adding mass was to use a more dense material. I had wanted to use a machinable tungsten but its expensive and i'm cheap. The next best option I could think of was using bronze or brass and making them slightly larger.

    I picked up a brass "drop" from ebay for $7 and started machining
    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]


    Once they were finished I weighed them and plugged the numbers into my spreadsheet.

    Custom wedges vs factory "heavy" wedges
    [​IMG]

    With that done i still needed to make the clutch cover. So i ordered a chunk of aluminum and got started.

    [​IMG]

    [​IMG]



    [​IMG]



    [​IMG]

    Once the cover was done I installed the clutch with the factory wedges and took it around my yard. as I expected it seemed like it could be more aggressive with the engagement.

    However being a tiny yard it was impossible to really evaluate so I left them in for the first test ride. (I was also worried the opposition springs were to weak for wedges 2x the factory weight.) I loaded up the bike and went to my local riding area. I took it out on a 16 mile rock loop I quickly noticed it was slipping a lot on the bottom and made it feel like a 250 (and made you ride it like a 250) the setup was way to revvy to for my liking.

    After i got back to the parking area I swapped in my custom extra heavy wedges.
    [​IMG]

    I was still very concerned the custom weights were going to overpower the springs. The worry disappeared as soon as I clicked into 1st and let out the clutch. It was a bit grabby at idle but the core is supposed to be. a quick function check every thing seemed good and then out into some more rocks. SUCCESS!! it grabbed when it was supposed to. You could ride a gear or two high without slipping. It felt like a proper 500... only it was impossible to stall. :clap
    #1
  2. anonny

    anonny What could go wrong?

    Joined:
    Mar 20, 2007
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    5,761
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    Beautiful Revelstoke BC
    Nice work, I assume this is for the engine that was stuffed into the KTM frame?
    #2
  3. jar944

    jar944 Been here awhile

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    You assumed correctly

    [​IMG]
    #3
  4. sailah

    sailah Lampin' it

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    Turning expensive metal into scrap
    That. That is awesome.

    I'll admit my eyes glazed over the math and I went right to the machining pics:D
    #4
  5. Pezz_gs

    Pezz_gs Cant ride for crap

    Joined:
    Nov 13, 2004
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    3,849
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    Sydney Skunkworks
    Brilliant work there!! :freaky

    So are you going to offer the wedges in kit form :evil

    I have a line on a CR500 engine and would love a Rekluse as I have one for my DRZ400 (462cc)
    #5
  6. jar944

    jar944 Been here awhile

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    Setting aside possible patent issues, I dont have enough time to get my own stuff done.

    Rekluse actually makes a auto clutch for the 500, but its the pro not the exp based core. Im just not a fan of th resulting lever feel or variable engagement point on those.
    #6
  7. davesupreme

    davesupreme grand poobah

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    palm harbor, fla
    very nice work!... :eek1
    #7
  8. voodoolord

    voodoolord n00b

    Joined:
    Oct 14, 2011
    Oddometer:
    1
    What year 500 engine is that? What year KTM? I have a 86 engine in a 90 cr500 roller that is absolutely awesome but I would love a Reckluse type clutch. I talked with them today and they said it wouldn't work for the 86 engine only 90+ but couldn't tell me why. Any ideas? Nice bike by the way.
    #8
  9. jimroid

    jimroid Been here awhile

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    Wichita Kansas-USA
    Nice job,I hope it works great for you!:clap:clap:clap
    #9
  10. jar944

    jar944 Been here awhile

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    752
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    Chantilly VA
    Its a 91cr5. in a 07 or 08 (I don't remember which) frame

    The 85-89 cr500's have a narrow clutch (compared to the later bikes) and the 85-88 have a 1 pc side cover. The recluse wont fit inside the case.
    #10
  11. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
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    Chantilly VA
    it works great.
    #11