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Blue Meanie and crank seals

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  • Blue Meanie and crank seals

    I'm not sure which section this should be posted in but here is as good as anywhere.
    I replaced the crank seals on my race bike "Blue Meanie" (MDS with 200cc Villiers kart engine) and have done about 6 sprint meetings since. Today at Houghton Tower, at the end of the second practice run it died then picked up again. After the first race run it died when I was slowing down and refused to start again. It has spit the cork gasket out from behind the clutch case and the gasket between the inner and outer clutch case.
    I guess the crank seal has gone again, pressurising the clutch case.
    I think I may need a different material for the seals. the methanol fuel must be attacking them. What is the best material?
    I should really have changed them every winter

  • #2
    The quick Silverstone riders were changing crank seals,primary chain and rings every meeting. Must admit I only did it every other meeting but others were faster. Dogsbody

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    • #3
      hi

      Have you thought about developing labarynth seals with piston rings ?


      gary
      Last edited by greeves246; 11/05/2015, 08:12 PM.

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      • #4
        EPDM and Nitrile seals should be pretty much methanol and ethanol proof.

        Is the seal actually failing, or just getting blow out?

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        • #5
          Originally posted by Andy Z View Post
          EPDM and Nitrile seals should be pretty much methanol and ethanol proof.

          Is the seal actually failing, or just getting blow out?
          Exactly Andy, there are a lot of stories & myths about ethanol & its effects but I have never come across any problems with it 'dissolving' oil seals, in fact I think it may have the positive effect of softening up older seals that have gone hard. My 4T engine does not have any adverse effect & its done over 25000 mile in my ownership alone without a seal change.

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          • #6
            The seal is failing enough to make it impossible to start the engine. Maybe the 11500 RPM red line isnt helping the seals. The fuel is Methanol, not petrol with Ethanol content.

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            • #7
              The rev range shouldn't be a problem. My son's KX60 runs at 12,000rpm with nitrile seals without any trouble. I wonder if lubrication is the problem, or lack of it. I imagine you're running a belt primary?

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              • #8
                No, duplex chain primary lubricated with auto transmission fluid

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                • #9
                  Have Simply Bearings not got any double lipped in the size you need ? They supply Viton seals as well, and the best prices on bearings. Dogsbody

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                  • #10
                    Originally posted by Dogsbody View Post
                    Have Simply Bearings not got any double lipped in the size you need ? They supply Viton seals as well, and the best prices on bearings. Dogsbody
                    I get mine from them too, mainly because they are totally reliable.

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                    • #11
                      I normally use Simply bearings too. I have ordered a set from Simon at Nametab because I am away from the bike this week and I didn't have the size to hand

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                      • #12
                        I'd steer clear of Viton seals, as they are not very resistant to methanol. The nitrile ones should be fine. I use the double lipped ones so that you can fill the gap with grease.

                        I would have thought Simon may be in a better position to offer further advice as not many bikes on here run methanol.

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                        • #13
                          I used to have to replace timing side seals every meeting on my 250 and 350 but drive side used to last pretty well. My advice is to make some labrynth seals .....they'll last years.

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                          • #14
                            I think my problem is drive side, it is pressurising the clutch case and spat the gasket out.
                            The drive side would be easy to make a labrynth seal, it could fit between the bearings in place of the aluminium stuffer

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                            • #15
                              We have always used labyrinth seals on our Oulton. They are a simple part turned from cast iron with Honda 50 piston rings. The sleeve in the crankcase is a cast iron part too. This was first done on our Oulton back in 1969! The picture shows this type of seal on the crank pulley after we converted to belt drive

                              Last edited by Oulton344; 25/04/2016, 08:27 PM.

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