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Scarry thoughts ~ bottom end rattle/s or what?

Discussion in 'Norton Commando Motorcycles (Classic)' started by Stuart SS, Sep 23, 2005.

  1. Stuart SS

    Stuart SS

    May 22, 2004
    How would you describe a bottom end rattle ? (OR ~ what is this sound!)

    I have a machine which is emitting a audible tapping on idle ~ which on the face of it sounds like it is coming from the primary cases !!!!!!!!!

    This tapping sounds more like rocker / tappet (single) rattle but is somewhat louder than the still audible rockers.

    By sticking a rod on the crankcases there is nothing to be heard ~
    but at the point of the timing access plug ~ there it is distinctive, even to the point that this the only place it can be heard via a 'rod' .

    The best description or comparison I would make would be my Ford EFI six cylinder which DOES have a cam follower which sometimes causes a tappet clacking on start up.

    This sounds exactly the same!

    (I realise that alloy cases are deceiving ~)

    The engine was rebuilt some 5,ooo miles ago ...

    I overhauled the primary about two weeks ago and replaced the clutch hub bearing ~ :shock:
  2. MichaelB

    MichaelB VIP MEMBER

    Jan 14, 2004
    Check the rotor. It may loose, tightens up on revs, knocks at idle.
  3. Stuart SS

    Stuart SS

    May 22, 2004
    EXCELLENT thought ~ MichaelB
  4. Jason Curtiss

    Jason Curtiss

    Jun 14, 2003
    And while you're in there, check the stator. I actually had a loose stator once and its symptoms were identical to what you've described.

  5. Stuart SS

    Stuart SS

    May 22, 2004
    Yes .. I am more than a little surprised I did not 'tweek' to this straight up .. well it was the day after the night before ~ 8)

    The fresh oil showed distinct signs of black deposits, which I figure were caused by the loose rotor ~???? :twisted:

    I had a look and tensioned up the rotor and checked the stator clearance , even removing and replacing it.

    The perplexing part is the the clearance at the bottom between rotor and the stator was quite large. where as the top was minimumal ~!!! at <.007>

    The stator is fairly new in fact , but the variance is of concern to me !

    (More great British quality standards? )

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