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1967 N15: spark plugs very very full of soot

Discussion in 'Other Norton Motorcycles' started by pierodn, May 25, 2018.

  1. pierodn

    pierodn

    Joined:
    Nov 10, 2012
    Hi.
    Idle works fine 1000 rpm with air pilot 1. 1/2 unscrewed and RPM on the stand go up and down quick without hesitate.
    Strange is that now only the left spark has soot.
    Can i go from cut 2 sliders to cut 3 or is it irrelevant?.
    Piero
     
    Last edited: Jun 2, 2018
  2. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    Piero

    I want you to turn left pilot air screw out to 2 1/2 or even 3 turns. This may not be good for idle, but if there is less soot, then we conclude idle circuit has a fault. if no change in soot, then we look somewhere else, and return idle air screw to 1 1/2 turns, until idle is properly adjusted as Triton Thrasher alludes.

    The slide cut away is not likely to be relevant.

    This problem reminds me of another thread, which, if my memory is correct, was posted by you. In that other thread, one cylinder was not firing. After 2 pages of replies suggesting what ignition tests to make, I suggested your mixture was so rich on that cylinder, it could not burn. Another member then suggested to check your pilot jet, and you found it missing!

    This problem seems very similar, but not as severe.

    Report back with soot test after opening pilot air screw.

    Slick
     
  3. Triton Thrasher

    Triton Thrasher

    Joined:
    Feb 10, 2009
    There is a time to stop arguing with helpful advisors like Mr Slick and do what they say.
     
  4. pierodn

    pierodn

    Joined:
    Nov 10, 2012
    Hi.
    Pilot jets 25 new.
    I will let younknow on monday.
    Piero
     
  5. pierodn

    pierodn

    Joined:
    Nov 10, 2012
    H
    Hi.
    Idle is fine.
    What it mean?
    May be better to replace the left carb?
    Thank you
    Piero
     
  6. pierodn

    pierodn

    Joined:
    Nov 10, 2012
    Hi.
    Forget to say that the bike has the air filter internal element of steel gauze.
    Can it cause a lean air mixture?.
    Thank you.
    Piero
     
  7. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    My Norton Owners Manual states:

    Amal 930

    Main Jet
    with air cleaner 220 (Atlas), 260 (650 SS)
    without air cleaner 240 (Atlas), 280 (650 SS)

    Pilot Jet 25

    Throttle Slide 3

    Needle Jet 107

    Needle Position Central notch

    An air cleaner tends to richen the mixture.

    Piero, your problem is a rich mixture on the left cylinder.

    Slick
     
  8. pierodn

    pierodn

    Joined:
    Nov 10, 2012
    Hi.
    I know this.
    But i dont know why!.
     
  9. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
    Yes they do drop out if not tightened, even.
    I would stop fluffing about and obtain a second-hand Gunson Colortune 14mm Kit Colortune Spark Plug Carburettor Mixture Tool and Here's a trick-use this only at night on a warm engine ;)
     
  10. pierodn

    pierodn

    Joined:
    Nov 10, 2012
    Hi.
    The left spark plug go on with soot.
    But the left exhaust when i close the throttle makes “mumble mumble” with high sound.
    Why?
    Air from exhaust or what?.
    Could be this the problem of such soot?.
    Thank you.
    Piero
     
    Last edited: Sep 25, 2018

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