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Thread: intermittent knock, Please help!

  1. #11
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    I just have never seen a serious knock that didn't keep knocking and get worse. Maybe something is slow getting oil to it.

  2. #12
    Senior Member TJones's Avatar
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    Quote Originally Posted by bmorgil View Post
    TJ what an eye! I went back and looked and thought the same thing, it looks like an arc on number one. Closer inspection and I think it's a piece of paper or tape flipping around.

    okiemark's suggestion (fuel pump) is also a very good thought. It sounds like it is timed with the cam. It could also be a sticking intake valve or a broken valve spring, letting the valve contact the piston. That would likely bend the valve and compression should be low on that cylinder.

    I thought the same thing on number 1 and I think it is paper or paint but number 4 is definitely an arc from the plug.



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    Last edited by TJones; 04-16-2020 at 10:05 AM.

  3. #13
    Super Moderator bmorgil's Avatar
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    My God Tim, how did you see that!? Definitely, you found it. The plug is grounding to the block. The arc is traveling down the electrode and across to ground on the block. We are hearing the fuel detonating in number 4. That plug must have a cracked center electrode. I had to put that up on the big screen to see it!

    monty509, pull that plug either the center electrode is broken or the porcelain is cracked. I think TJ found it for sure.

    TJones "Eagle Eye".

  4. #14
    Senior Member TJones's Avatar
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    Actually I BLEW it up like you did and kept hitting the replay on my office computer and sure enough it's a arc.

  5. #15
    Super Moderator LarrBeard's Avatar
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    Cracked insulator on # 4

    Quote Originally Posted by TJones View Post
    I thought the same thing on number 1 and I think it is paper or paint but number 4 is definitely an arc from the plug.



    IMG_2060.jpgIMG_2061.jpg
    There may be several things going on, but throwing the plug in #4 as far as you can is the first and simplest fix to try.

    Great eyes TJ!

  6. #16
    Super Moderator gmwillys's Avatar
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    Easy things first. Great catch TJ!

  7. #17
    Senior Member TJones's Avatar
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    The only reason I kept looking at the video was it didn't really sound like a rod,valve,wrist pin or anything metal knocking around it was more of a muffled sound like a misfire or something.
    Maybe it's not the plug but it's a lot cheaper and easier to replace a fouled/broken plug then jerking it all apart.
    Believe me I have heard plenty of motors have Scrap Iron Fits and this one didn't sound to bad at all!!
    Last edited by TJones; 04-16-2020 at 02:22 PM. Reason: Stupid Spell Check I guess, or poor grammar or BOTH

  8. #18
    Super Moderator LarrBeard's Avatar
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    Mark Up One For The Old Guys!

    Quote Originally Posted by TJones View Post
    The only reason I kept looking at the video was it didn't really sound like a rod,valve,wrist pin or anything metal knocking around it was more of a muffled sound like a misfire or something.
    Maybe it's not the plug but it's a lot cheaper and easier to replace a fouled/broken plug then jerking it all apart.
    Believe me I have heard plenty of motors have Scrap Iron Fits and this one didn't sound to bad at all!!
    Every so often the blind squirrel finds an acorn without a worm in it!

  9. #19
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    I pulled the plug no real visible damage to it besides some small chips on the very to of the insulator. The plug has quite a bit of dry fouling though, maybe that's causing the ark, insulator not being able to insulate? We will find out Sunday when my gaskets get in and I put it back together. I got some new plugs. Maybe i'll put it back in and run it in the dark and see what it does. Thanks for all the help, very kind.

    Also when I pulled it out there was a very strong smell of gas.
    Last edited by monty509; 04-16-2020 at 06:28 PM.

  10. #20
    Senior Member TJones's Avatar
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    You are very welcome monty509, the smell of gas makes me think it may be the plug even more but the thought of running it in the shop/garage in the dark will be the answer.

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