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Thread: Clutch slave cylinder seal. Again.

  1. #1
    apriliaforum expert dipso441's Avatar
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    Clutch slave cylinder seal. Again.

    Thought I read on here that one of us in UK had found a clutch seal that is more durable (& cheaper) than oe.
    Did a search but can`t find it.
    Was it all a dream?

    Cheers, dipso441

  2. #2
    apriliaforum expert chrisonord's Avatar
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    Cheaper yes.....
    More durable........nah.
    Redgold hydraulics are the people to get them from though, the more you get off them the cheaper they are. I got 2 for 15 quid a couple of years back.
    Chris.

  3. #3
    apriliaforum expert GRUMPYGIT's Avatar
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    You should be able to get a seal from any good hydraulic dealer. The sort you want is a UP20-28-4. Steve

  4. #4
    apriliaforum expert dipso441's Avatar
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    Many thanks Chris & Grumpy.
    See you in Llandovery.

    Cheers, dipso441
    Last edited by dipso441; 05-25-2011 at 02:30 AM.

  5. #5
    apriliaforum expert falcojake's Avatar
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    i got a rsv1000 seal from my local aprilia dealer for 10.

    i guess i could have got a generic wiper seal for a lot less than that but it was a saturday and i wanted to ride my bike on the sunday.

    however, i have a theory. having had the same problem on my falco and in both cases the clutch fluid dissapeared while the bike was left standing for a few weeks. when i changed the seal on my caponord there was little wear on it. in the case of my falco i blead the clutch and rode the bike for weeks without a problem i took the bike for a service and asked them to replace the seal as i was going on a trip to italy after that. (when i worked abroad and had money to waste on dealer services)

    anyway i think that the seal is a wiper seal that flares out or inflates under the hydraulic pressure, there is no spring like you would find on a bearing seal to keep the seal tight against the bore of the cylinder. i recon if the cylinder is bled and pressurized it will run again until it is left to contract and leak. just a theory.

    i recon the best policy is to get an oberon cylinder and have done with it! but bleeding the clutch will give longer service to the seal again

  6. #6
    apriliaforum expert chrisonord's Avatar
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    I bled and re bled mine several times but it ended up getting that bad I just went the Oberon slave cylinder route. As well as reliability, the clutch lever is smoother and lighter to operate, which is always helpful when using short levers.
    Chris.

  7. #7
    apriliaforum expert the_toe_cutter's Avatar
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    My clutch slipped ever so slightly under the hardest of accleation with the oberon until i adjusted the lever all the way out. The oberon givith and taketh away lol. Greased the seal (and bore, i know i know) with silicone and the fluids remained clean and clear! A first on the 3 'rotai' ive owned.
    Brum Brum

  8. #8
    apriliaforum expert dipso441's Avatar
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    I just bought 2 x POLY U 28-20-4 seals from
    ATL Hydraulics Ltd
    18 Kingsley St
    Leicester LE2 6DL.

    3.46 for two inc VAT, against 11.98 + VAT EACH on the Aprilia parts list.
    If these are correct fitment & successful, I`ll post on the `Parts Suppliers` sticky above.

    Cheers, dipso441

  9. #9
    apriliaforum expert JohnG.'s Avatar
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    Quote Originally Posted by the_toe_cutter View Post
    Greased the seal (and bore, i know i know) with silicone and the fluids remained clean and clear!
    Yup,assemble with silicone grease...
    I flush/bleed my oem slave cyl. every six months for long life
    Fluid is usually very black/grey by then at the slave.
    JohnG.

    '02 Capo.

  10. #10
    apriliaforum expert dipso441's Avatar
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    500 miles on from fitting & the POLY U 28-20-4 works fine.
    Many thanks, Grumpy.

    Cheers dipso441

  11. #11
    apriliaforum expert the_toe_cutter's Avatar
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    One for the tool kit so, nice work Grumpy and Dipso we will bash these bikes into shape yet !
    Brum Brum

  12. #12
    apriliaforum expert GRUMPYGIT's Avatar
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    Quote Originally Posted by dipso441 View Post
    500 miles on from fitting & the POLY U 28-20-4 works fine.
    Many thanks, Grumpy.

    Cheers dipso441
    Glad to hear it worked Dipso and at a fraction of the price of the Aprilia one. Cheers Steve

  13. #13
    apriliaforum expert Capoandrew's Avatar
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    Been lurking over the post and read Falcojake's take on things. Reminded me of the KTM 950A. They had exactly the same issue. Slaves failing on a regular basis. Some guys replaced seals, others went the Oberon route.
    For me personally, I had no issues over 60,000kms. (nada, zip, zilch) However, I replace the fluid every 5000km religiously.

    I see John has had a good run. Go figure??!!

    Is this just another QC issue or design issue for Aprilia (or more likely the manufacturer of the slave?)


    Mods (so far): Aprilia Rally Raid bars, bar clamp, seat, rear shock absorber, suspension link, front guard, headlight stone guard and lower chain guard. Replica RR sump guard. Leo Vince exhaust, Catfish Mapping. Mk2 Top fairing, painted to match. MG hand guards. Aprilia Dorso indicators. Honda CBR600 Reg. Autocom Intercom. Aux fuse block. H&B side racks. Trax Evo panniers. Tourfella top box Palmer aux bracket. BMW GPS quick release mount. Cyclops LED spot lights. Anakee 2 Tyres. And probably something else I can't think of right now!

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  14. #14
    apriliaforum expert dipso441's Avatar
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    Unlike Jake`s bike, mine had been in daily use when the seal went/fluid disappeared.
    It sits over winter with fresh fluid & the inside of the slave cylinder was fine. Wear on the seal seemed equal all round, so the piston was sliding square in the bore.
    It`s an `01 bike with 13k miles. The old seal was much softer than replacement, so maybe it`s an age or temperature thing. The slave cylinder is too hot to touch for long once the engine is at working temp. Maybe not the best environment for a rubber(?) seal.
    Perhaps a slim asbestos gasket between crankcase & slave cylinder might extend the seal`s life.
    Then again you`d expect John`s bike to run hotter in his tropical neck of the woods, so I may be talking pants.
    Anyway I`ll report on whether the replacement seal lasts more miles than oe.

    Cheers dipso441
    Last edited by dipso441; 05-26-2011 at 04:27 AM.

  15. #15
    apriliaforum expert the_toe_cutter's Avatar
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    Its been said that the comination of small resevoir volume, heat and type of alloy thats used in the slave causes the fluid to blacken. Some have gone on to say the blackening of the fluid was tiny debris from the seal itself, not sure on that personally. Alls i know is i greased mine and its remained crystal for over 8 months now (yes the oberon had the fluid darkening issue also).

    Here was my old seal original with about 18k on it,
    Click image for larger version. 

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    Still am not sure if the replacement i sourced with a revised pt no was going to last longer, anyone comment on this item over the old? ( i ask as i swapped it with CC's oberon)
    Click image for larger version. 

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    Im not an hydraulics expert but i can see the blackening of the fluid as being a reason for why the seal shit itself?
    Here was my old one with just a summers worth of riding
    Click image for larger version. 

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    Brum Brum

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