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Thread: Diagnosis of clutch unhappiness

  1. #1
    apriliaforum expert photoRotor's Avatar
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    Diagnosis of clutch unhappiness

    On the way home from a 150-ish mile ride, and the clutch lever started feeling a little "soft". By the time I got home, the lever was only working in about the last 1" of travel. Fluid is a couple of years old, and at the right level.

    So, is it likely the master cylinder on the handlebar, or the slave, and how do I diagnose that? I suspect it's the master, and if it is, has anyone switched to the RSV-R master and reservoir?
    JD

    Futura
    Bunch of dirtbikes

  2. #2
    apriliaforum expert deefred's Avatar
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    Bleed the clutch first.
    When holding the clutch lever in to the handlebar and you feel after a while the force to hold it is reduced, the master is bad.
    Happend to me. Ended up getting Ducati coffin style radial masters. The older mille has the same piston in the master so find a crashed one and just take the piston. There is a company in england selling seals (search the forum) but installation of them is a bit tricky.
    2001 RST Futura in stream Silver.
    Mods: Modified Öhlins fork from mille R, EBC 320mm brake discs, HEL front brakelines, Carbon RS 250 front fender, Wiring mod for charging. Engine related:05 map, Iridium plugs, tuneboy, derestriced intake, old mille airboot, staintunes exhaust. Lambda bung hardbrazed in the "breadbox". Öhlins mille R rear shock with 110N/mm spring and the integrated hydraulic preload adjuster. LED Voltmeter installed inside the dash for monitoring charging. Duc 999 radial m/c for brake and clutch.
    NWS hugger. Equipment: Famsa tankbag,
    CBR 600 -07 MOSFET R&R FH008EE providing stable 14.4 - 14.5 V (with my wiring mod). Daytona heated grips with mccoi pwm controller and automatic chain oiler

  3. #3
    apriliaforum expert photoRotor's Avatar
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    Will do - thank you
    JD

    Futura
    Bunch of dirtbikes

  4. #4
    apriliaforum expert spesnaz's Avatar
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    Our OEM Brembo clutch master cylinder is a unique one, as it holds about 5cc of fluid. Problem is that the diaphragm / reservoir cover seal takes up 90% of the area in that reservoir. Like Deefred suggests, bleed this system first, you'll find some really nasty fluid in there.

    The piston seal could be worn, allowing a bit of air to enter the system. Best method to bleed the clutch system is to rotate the handlebar so the reservoir is level. Place a drop cloth of fender protector, beach towel, or a pillowcase if the wife isn't looking, over your fuel tank, instruments, and the acrylic windscreen.

    Clean both sides of the diaphragm, you'll find the "upper" side will have wet nastiness (condensation) as well.

    You'll find that Brembo designed this master as an homage to mighty Vesuvius, be really careful during that first few millimeters of lever travel! As the bypass port is open, she'll erupt brake fluid like crazy. To access the bleeder, remove the left fairing covers.

  5. #5
    apriliaforum expert photoRotor's Avatar
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    ^Great info as always - gonna be a few more days before I can get to it, but will report back.
    JD

    Futura
    Bunch of dirtbikes

  6. #6
    apriliaforum expert spesnaz's Avatar
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    Good stuff! If your external dust seal is tearing, by the way, look up this part in the RSV mille section. It's not listed separately in the Futura section, though the dust cap is the same Brembo part.

    I bleed the clutch every few months, it goes black in nothing flat. Clutch feels awesome with a fresh fluid change.

    Bob

  7. #7
    apriliaforum Member
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    https://www.af1racing.com/store/Scri...idProduct=2382

    Pull the clutch slave, replace the seal, bleed all the old nasty fluid out, happiness is a smooth, progressive, clutch.
    '02 with lots mods: full race airbox, evo filter, mille intake, H-pipe, staintunes, PCIII, Carbon Hugger,Custom Gloss Black Paint, Custom silver powder coated wheels and other bits, Billet aluminum (well O.K. Home Depot Aluminum Strap) Pivot Covers, Throttlemeister. Looking for full radar and laser stealth technology!

  8. #8
    apriliaforum expert photoRotor's Avatar
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    Thanks guys. Been busy of late as my Dad passed away recently, but I'll report back once I get it fixed.
    JD

    Futura
    Bunch of dirtbikes

  9. #9
    apriliaforum expert Futura's Avatar
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    Here we go again.

    Putting some eyes on the underside of my clutch slave, it is dribbling again, as seems usual.

    It has not emptied the reservoir after about 1 year, but clearly leaking.

    I have never been able to stop the slave from leaking.

    It has a fresh, new seal as of 18 months ago, and the cylinder walls are flawless.

    It was cleaned well, and bled out carefully then.

    Still a great mystery why these things leak.

    I am using Valvoline DOT 4 synthetic fluid.

    Stock Aprilia seals from AF1.

    I wonder if somehow daily temperature variations create a small but constant pressure, pushing the fluid past the seal.

    Is there perhaps a seal from another brand of bike which might behave better?

    Also, are there any crosses for the clutch master seals, or the front brake master seals?
    Last edited by Futura; 03-11-2019 at 01:35 AM.

  10. #10
    apriliaforum prov-nov
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    Are you sure its not oil drippling down ? I was getting a small leak from same area and it was the seal for the clutch rod. I replaced the clutch rod as it was showing some wear as well as the bearing and seal and no more dribble.

  11. #11
    apriliaforum expert Futura's Avatar
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    Quote Originally Posted by ga. grizz View Post
    Are you sure its not oil drippling down ? I was getting a small leak from same area and it was the seal for the clutch rod. I replaced the clutch rod as it was showing some wear as well as the bearing and seal and no more dribble.
    It may well be the pushrod seal. It was not clear with all the grunge. I will keep an eye to try to determine.

    Of note, the clutch had not leaked down since last year, so very possible it is the pushrod seal.

    Just placing the breadbox back after replacing exhaust gaskets, so took the time to clean off the bottom side.

    Seemed like DOT fluid at the moment, but we shall see.

    Thanks...

  12. #12
    apriliaforum newb
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    After chasing seals for my Futura "Brembo" Master cylinder I can confirm the following part numbers.

    The actual dimensions of the Master piston/bore it is to fit is 12mm od x 7mm id x 4mm SU12-7-4-EP-DS106 IS CORRECT


    The actual dimensions of the Master piston/bore it is to fit is 12mm od x 5mm id x 4mm SU12-5-4-EP-DS106 IS CORRECT

    The actual dimensions of the Slave piston/bore it is to fit is 28mm od x 20mm id x 4mm wide SU28-20-4-EPDM-DS106 IS CORRECT

    The suppler is FPE Seals Ltd, 7 Barrington Way, Darlington, County Durham, DL1 4WF, England.

    The staff are extremely helpful.

  13. #13
    apriliaforum Member zag07's Avatar
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    It help with some pics : https://www.apriliaforum.com/forums/...-Seals-Sourced Then replace "grey" DOT liquid & bleed & bleed again .....

  14. #14
    apriliaforum expert photoRotor's Avatar
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    Forgot about this thread... bled (burped) the clutch a couple of months ago, and everything is happy again.
    JD

    Futura
    Bunch of dirtbikes

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