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Strange Engine Noise - Rod Knock?

Discussion in 'Norton P11 Motorcycles' started by elefantrider, Jul 7, 2019.

  1. elefantrider

    elefantrider VIP MEMBER

    Joined:
    Apr 6, 2013


    Following up on an old problem, I had believed this intermittent grinding noise was the primary chain master link hitting one spot on the inner chain case. But after observing the chain running with the cover off, I determined the chain was not hitting the inner case at all. I think this noise is internal to the engine.

    Has anyone else heard similar noises in their engine and identified the source?
     
    Last edited: Jul 8, 2019
  2. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    Cam chain or magneto chain?

    A rod knock would be more rhythmic.

    Slick
     
    Last edited: Jul 7, 2019
  3. elefantrider

    elefantrider VIP MEMBER

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    Apr 6, 2013
    Maybe, but it doesn't make this noise on decel when riding. Will remove the timing cover and see.
    I am reluctant to ride any distance and speed with that strange noise.
     
  4. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    My first guess would have been primary chain like yours, but as you said you had cover off and found chain not hiiting inner cover.

    It could still be the primary chain hitting stator or stator mounts. Did you actually run the engine with the cover off? If so, did the noise cease when you ran the engine with the primary cover off?

    My Atlas will tick the stator mount if the chain is loose. I know your stator config is different, but this illustrates the chain has a great deal of up/down motion.

    The noise ceasing on decell would indicate it is the lower chain run that is the culprit.


    Slick
     
    Last edited: Jul 8, 2019
  5. elefantrider

    elefantrider VIP MEMBER

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    Apr 6, 2013
    Yeah, I ran it without the cover, and the noise was still there. The chain is definitely not hitting the inner cover anywhere. The noise gets louder when I pull in the clutch, so I think it is clutch- related. What could cause the clutch assembly to make that noise?
     
  6. texasSlick

    texasSlick VIP MEMBER

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    Jan 2, 2013
  7. elefantrider

    elefantrider VIP MEMBER

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    Apr 6, 2013
    Thanks Slick, I pulled off the basket and noticed the following. The clutch center splines are worn badly (grooved), and the backplate turns uneven, wobbles. All the rollers are in place however. Clutch has new rubber.
    Maybe it is the uneven backplate.
     
    Last edited: Jul 8, 2019
  8. texasSlick

    texasSlick VIP MEMBER

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    Jan 2, 2013
    NOTE!

    The race plate (Item 4) is drawn backwards in the clutch exploded parts diagram!

    Perhaps the PO followed the pics and put it in backwards. This might cause the wobble you see. In any event, be sure to flip the plate over when you assemble.

    Slick
     
  9. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    It sounds like a loose piston to me. After a light seizure or a piston with a collapsed skirt. Jim
     
  10. elefantrider

    elefantrider VIP MEMBER

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    Apr 6, 2013
    Screwdriver handle to the ear gives no clue in pinpointing the noise to the engine.
    I took the primary covers and clutch off, and reinstalled - noise still there. Noise gets louder when clutch is engaged (lever pulled in), and seems to have the exact same rythym as when the clutch is disengaged (lever out).

    Sounds like a Ducati clutch! Are Atlas clutches THAT noisy without fluid?

    I could lift the cylinder with the head still on, and check the pins and piston skirt.
    Oil does NOT have any metallic particles so I am trying to eliminate everything else before I tear into the engine.
     
  11. Pushed it n rode it

    Pushed it n rode it

    Joined:
    Jun 10, 2019
    Try some ATF in the primary ! My 650 sounded dreadful and is a fair bit quieter when I engage the clutch since I changed to it.
     
  12. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    Does the noise diminish if you are holding the clutch in and put it in gear?

    And short one plug wire at a time and see how it changes.
     
  13. elefantrider

    elefantrider VIP MEMBER

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    Apr 6, 2013
    Noise definitely diminishes with the left cylinder plug shorted. (note to self: need to get insulated plug wire pliers!!)
    No noticeable change when right plug wire is pulled, or with clutch in and trans in gear, although hard to tell - noise is masked by the noise of the clutch.

    Sounds more and more like I'll be pulling the head and barrel soon.

    Pistons are stock atlas, low compression.
    If piston was loose or cracked, I would expect blowby or smoke.

    Maybe its valvetrain?
     
    Last edited: Jul 15, 2019 at 7:15 PM
  14. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    I would be suspecting a piston -or wrist pin problem.

    Another thing you might want to check first would be to pull the chaincase cover and see if there is excess up and down play in the left end of the crank. But I doubt that's it from what I hear.

    I don't think I would want to run it any more without taking a look. Jim
     
    motorson likes this.
  15. motorson

    motorson VIP MEMBER

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    Nov 29, 2011
    Sounds like a loose piston to me too. I've had one make that same sound and it was the skirts being galled from a "soft seize." Having the timing too far advanced will cause that kind of damage too if it is run that way too long.
     
  16. jerrykap

    jerrykap VIP MEMBER

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    Jul 23, 2014
    Other possibke noise sources? Pushrod end has come loose and broken valve spring. All require dissasembly. Good luck.
     
  17. elefantrider

    elefantrider VIP MEMBER

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    Apr 6, 2013
    I will tear it down this weekend and let you know.
    There is not any up and down play on the crank.
     
  18. jbruney

    jbruney

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    Jan 5, 2019

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