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Primary leaks

Discussion in 'Norton Commando Motorcycles (Classic)' started by htown16, Apr 16, 2018.

  1. htown16

    htown16 VIP MEMBER

    Apr 29, 2009
    I have a dribbling primary on my recently rebuild 74. Use ATF so only one place the red stuff can be coming from. Looks like it is coming from the bottom seam between the inner and outer cover. I'll take it apart and clean and check for flat. I carefully shimmed the inner cover when I built the primary.
    I installed the rubber band seal with no sealer. Is it a good idea to use a sealer and if so what.
  2. ashman


    Jul 11, 2010
    Do not over tighten your outer primary case or it will leak, is it a new sealing rubber or old one.

  3. 84ok


    Aug 10, 2014
  4. texasSlick

    texasSlick VIP MEMBER

    Jan 2, 2013
    Here is more discussion re: seals in the primary:


    I have no leaks in an Atlas primary ...... If that can be done, the Cdo is a piece of cake.

    Check also, the gasket between the inner primary cover and the drive side crankcase. If you can find 1/32" thick synthetic cork or reinforced silicone gasket material, make your own gasket from those materials. BTW, those materials make an excellent sealing washer between the discs.

  5. 84ok


    Aug 10, 2014
    i haven't run across a confirmed fix for commando primary cover (rubber band seal mentioned op) O ring leak other than the above link,

    even if there is, another issue mentioned by others for going belt drive is clutch slippage issues (dunno the details) with the chain/oil drive setup
    Last edited: Apr 17, 2018
  6. robs ss

    robs ss VIP MEMBER

    Aug 16, 2016
    Slick - sorry to be a bit thick - what discs are you referring to?
    If it's the ones at the primary shaft I wasn't aware they could be removed and gasket material added.
  7. 84ok


    Aug 10, 2014
  8. concours

    concours VIP MEMBER

    Dec 29, 2011
    My '74 primary is OIL TIGHT. Shimmed correctly on the center stud, black (VERY oil resistant) RTV applied around the stud, stator wire grommet, trans seal sheet metal housing, and, in the groove before the giant o-ring. Also, on top of the o-ring. Nipped up, RTV wiped tidy.
    I WAY OVERFILL the case with ATF (bottom chain run completely submersed).
    No drips. At all.

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