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Sealing washer, timing side bearing WHY??

Discussion in 'Norton Commando Motorcycles (Classic)' started by Fast Eddie, Jan 10, 2019.

  1. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    Whats the reason for the sealing washer that goes in next to the timing side main bearing?

    Meaning, why does it need sealing, and from what?

    Why not just let the head oil return through the bearing into the crank case?

    My reason for asking is that my Maney cases have no holes from timing chest to crank case. I’ll be running a cNw / Comnoz breather on the back of the case.

    I am about to drill the ‘Comnoz oil return hole’ just below the pump and got to wondering why not just allow oil to return through the bearing?

    I’m pretty sure there’s a sound reason for this that I’ve overlooked... can someone please enlighten me?
     
  2. Dommie Nator

    Dommie Nator VIP MEMBER

    Joined:
    Apr 2, 2013
    I thought I had read it somewhere recently, Comnoz said

    "You don't want to leave the washer out. The bearing could be flooded with oil from the timing chest which will cause the bearing to fail at high speeds. Jim"
     
  3. Fast Eddie

    Fast Eddie VIP MEMBER

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    Oct 4, 2013
    Thanks Cab.

    But my next question is, why would flooding a bearing with oil cause it to fail?
     
  4. L.A.B.

    L.A.B. Moderator VIP MEMBER

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    Nov 20, 2004
  5. baz

    baz VIP MEMBER

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    May 26, 2010
    From what I have read about racing BSA b50s and later on CCMs is that too much oil to the big end (rollers) can cause the bearing to over heat and fail
    Maybe it's the same for main bearings?
     
  6. Fast Eddie

    Fast Eddie VIP MEMBER

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    Oct 4, 2013
    Right, got it!

    Thanks gents.

    The washer stays, and I’ll be drilling a new oil drain hole, like a good boy !
     
  7. Hortons Norton

    Hortons Norton

    Joined:
    Oct 12, 2007
    I think it will also start to skate???
     
  8. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    Yep, too much oil and a roller will stop turning and hydroplane when the load is light. Then when the load returns it skids as it comes back up to speed and you get excess wear.
     
    Fast Eddie likes this.
  9. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    Thanks Jim, how is that overcome in applications of pressure fed roller big ends? Which I guess is linked to Baz’ pint above. How can you have too much oil to a pressure fed big end? Surely it’s going to be flooded no matter what you do?
     
  10. ntst8

    ntst8 VIP MEMBER

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    Feb 14, 2004
    Freudian slip perhaps, i'm enjoying a cold one at the moment. :rolleyes:
     
    blaisestation likes this.
  11. concours

    concours VIP MEMBER

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    Dec 29, 2011
    Oil discharge orifice diameter controls volume.
     
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  12. kommando

    kommando

    Joined:
    May 7, 2005
    Plus the size of the feed gears is changed, normally reduced in width on roller bearing engines vs shell bearings.
     
    Fast Eddie likes this.
  13. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008
    Yea, careful control with orifice size and pressure.
    The same thing happens if you overlube the roller bearing in a big end.

    That is also why a sealed ball bearing only comes packed with a small amount of grease.
    If you overpack it and then run it fast, they will fail early.
     
    Last edited: Jan 11, 2019 at 7:43 AM