preignition spark knock
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Thread: preignition spark knock

  1. #1
    Senior Member plumbstraight's Avatar
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    Mar 2013
    Montesano, Washington

    preignition spark knock

    I have noticed my 09 has an issue with spark knock. I have a 95 and sold my 03 and neither one of them had the issue like my 09. I think I need to back off the advance on the spark. Is this possible on the TW or is it set from factory? If I lug it at all, or try to take off on a hill it complains.

  2. #2
    Senior Member Tweaker's Avatar
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    Dec 2015
    San Diego
    I am pretty sure it is set. Mine were doing that when I first got them but it was because of the DG pipes. Rejetting fixed it. Maybe your main jet is glogged. I pretty sure mine was a lean problem.
    BTW we are talking about flying up to see you in ALaska.
    Fred, ejfranz, grewen and 2 others like this.
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    Twin 2014 TW200's made side by side on the assembly line, Moose rear racks, Protaper ATV high bars, DG oval pipes, kick starters, rejetted carbs, 130 main jets, 2 -3 -.020 shims on the needles and @ 2 1/2 turns on the pilot screw, #34 pilot jets, Acerbis hand guards, Shinko 241 front tires, modified Krator foot pegs, 14-55t sprockets, Ricochet skid plates and 90 degree fuel filters.

  3. #3
    Senior Member Fred's Avatar
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    Dec 2011
    Turtle Wrangling the Sierras
    Effective timing can change slightly with a loose cam chain adjuster. Perhaps pull cam gear cover and crankcase inspection port off in order to inspect timing marks and chain tensioner? With chain tight the correct witness marks should all align, if loose timing can drift up to about 1/2 a cam tooth. If chain appears at all loose pull the auto-tensioner and inspect/clean/wind up and release for a test,etc...

    This assumes the problem is indeed a pre-ignition issue and not old fuel or carberation related.
    Last edited by Fred; 03-01-2019 at 10:08 AM.
    Tweaker likes this.
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  5. #4
    Super Moderator Purple's Avatar
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    Mar 2015
    Ynys Môn
    Not adjustable - the timing is set by the chain - so I'm with Fred on this one .....
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  6. #5
    Super Moderator JerseyJeeper's Avatar
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    Mar 2011
    NJ Shore / Pine Barrens
    Fuel in this mixture has two jobs:

    1. Explode and turn the crank..

    2. Cool the piston crown and cylinder walls etc. [Remember evaporation cools the surface]

    So some part of the fuel that is pushed into the cylinder actually cools it a bit. When you go lean what happens is that with every progressive stroke the cylinder / piston etc gets hotter as the cooling effect of fuel is less due to a lean mixture

    Thereby you can get Hot-Spots in the cylinder / Piston and as the fuel air mixture is compressed this Hot spot can lead to a pre-ignition, and a very lean mixture can take the damage further and sometimes hole the piston

    A slight increase to richer in mix may help (adjust the screw).

    But it could be anything.. including you are in-fact loading the little motor a bit much.
    admiral and plumbstraight like this.
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  7. #6
    Senior Member elime's Avatar
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    Jul 2010
    San Jose, CA
    Camshaft timing is controlled by the chain.

    For spark timing, the initial advance is set when made and then further advance is by the CDI.

    There is no adjustment for the initial spark timing. At higher RPMs Tom Bauer can change the timing advance curve in the CDI or you can buy an Igni Tech CDI with adjustable spark timing you can change with your laptop.
    Long live the internal combustion engine!

  8. #7
    Ken is offline
    Senior Member Ken's Avatar
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    Aug 2016
    Houston, Texas
    I would try 95 octane if enriching the carb doesn't work and your timing lines up correctly. I had a car I increased compression on, cam change etc. It loved Valero gas. Everything else would ping and it was running rich.
    elime and plumbstraight like this.

  9. #8
    Senior Member plumbstraight's Avatar
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    Mar 2013
    Montesano, Washington
    When the crew arrives at Moab I will have one of you guru's check it out for me. I have never messed with the needle or screws on the carb.
    Tweaker likes this.

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