What's That Horrible Noise Quiz :(

Discussion in 'Technical Help' started by Nelson, May 19, 2017.

  1. Sounds like the left side main bearing to me
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  2. What am I looking for once the case is off?
    Is the main viable for inspection?
  3. Nelson, there will probably be up and down and side to side (across the crankcases aka end float) motion on the crankshaft. The bearings are supposed to have an axial preload. Did you get anything out of the strainer?

    Good luck on this, I hope for your wallets sake its something else
  4. Rough running was a failed spark plug. Why now!
    Casing is stuck fast! Too fast for my home made bodged tool...Just ordered a new one.
    Bastard thing!
  5. Make sure you have undone the sneaky bolt around the clutch slave - or your new tool will just crack the cover - usually hidden under chain lube . Gunk
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  6. With clever use of the clutch slave I've managed to pop the casing off.
    Water pump bearing feels ok.
    The small crank end/stator/alternator bearing does feel a little notchy, new one on order along with some threebond. (hate threebond)
    No massive play on the flywheel, however I'm not too sure there would be unless there was catastrophic failure?
    Thanks for everyone's help:)
    All bits crossed :mask:
  7. There shouldn't be any play in any plain in the flywheel chap.

    Steve R
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  8. Modern Ducati motors use waaay too much preload IMO, resulting in main bearing failures since the advent of the 999's.
    On the advice of John Hackett quite a few years ago now, I use only 4 thou preload on the mains in my motors and...
    I've never had a main bearing failure.

    Steve R
  9. Could you explain what this means (at a very very low tech level) please?
  10. The pre-loaded pressure (squeeze) on the bearing when assembled in the casings. I assume if this is too great when the different metals (bearing/casing) heat up and expand this will put pressure on the bearings and cause premature failure.
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  11. Had that and it knocks...
  12. Nelson as the engine heats up the preload gets less as the casings expand but the pair of bearings have to have just a little prelod to operate properly at running temp, that hot running preload is specified by the bearing manufacturers. If you put a typical 0.2mm preload cold that will mostly disappear as the engine heats up which is why there should be no float or up and down play when cold. Steve R and John Hackett is suggesting 0.1mm is more appropriate

    CR the mains are a pair of facing angular contact bearings which are "clamped" together by the crank cases and shimmed to ensure they retain the correct axial loading they are designed to operate with. Too much axial load means the bearings will break down due to overloading, too little means the bearings run loose and break down due vibration and intermittent ball loading. They are designed this way to minimize engine construction costs by reducing the tolerances required making the crankcases the perfect size.

    This is an extract from an skf bearing catalogue, the crankshaft is arranged with a pair of bearings arranged "face to face" either side of the assembled crankshaft

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  13. Thanks Denzil,
    Very useful info.
    Poor choice of words post #26. No play detected on the fly wheel. If it was a major failure I'd have thought there would be some, if wearing/noisy maybe none/none till warm.
    The little bearing I have pulled is definitely showing signs of wear and was noisy when listened to via the big screwdriver.
    Whether or not that was 'the' noise I'll have to wait and see once I have re-assembled.
    If it is the main(s) I have some decisions to make re the future of the bike :(
  14. Fingers crossed....
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  15. I've swapped out the little bearing in the l/h case,which was a bit notchy, I was also surprised how not tightened (wouldn't say loose) the three screws were holding the stator in where, these have been tightened and threadlock added.
    Ran her up to temp a few times and the noise appears to have gone...:) I'm taking her to Silverstone next Monday, so lets see what a sound thrashing does...:upyeah:
    #35 Nelson, May 26, 2017
    Last edited: Jun 20, 2017
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  16. Great news :)
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  17. Nice one, what a relief.
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  18. Nelson, great news:upyeah::sweat:
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  19. :upyeah::upyeah:
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  20. Happy to report (temps fate) that a after two sound thrashings (track days) all appears well. :cool:
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