Start-up/Shut-down knocking

Discussion in 'Lawn Mowing' started by sethsodsquad, Nov 22, 2004.

  1. sethsodsquad

    sethsodsquad LawnSite Member
    Messages: 182

    Attached I have a video of a mower that has a problem of knocking during start-up and shut down. The sound is most noticeable during shut-down in the video clip. When the mower is running, the sound is there, but not as loud.

    I can't figure out why it's making this noise, or even where in a specific area it is making this noise. :angry: It isn't the crankshaft I believe because the mower doesn't have any excessive vibration.

    This engine is a B&S Intek 6.5 hp. It is on a JD, which isn't that important to the problem.

    Just wondering what you all think the problem is. . . .

  2. specialtylc

    specialtylc LawnSite Bronze Member
    Messages: 1,656

    My guess is its in the BBC, bearing going out or blade is loose. I have had similar problem with JD and Honda 21s. My expierience with JDs is they have a poor BBC design. Early bearing failure and really small clutches.
  3. sethsodsquad

    sethsodsquad LawnSite Member
    Messages: 182

    The John Deere JS63 doesn't have BBC and the blade is very tight.


    Attached Files:

    • jd.avi
      File size:
      1.8 MB
  4. FrankenScagMachines

    FrankenScagMachines LawnSite Platinum Member
    from IN
    Messages: 4,739

    hmmm... by the sound i'm almost wondering if it maybe something to do with the valves, but it runs pretty smooth if thats really the problem.. let me think on this a bit...
  5. Eric 1

    Eric 1 LawnSite Bronze Member
    Messages: 1,220

    What did you use to open it, the media player wont work.
  6. FrankenScagMachines

    FrankenScagMachines LawnSite Platinum Member
    from IN
    Messages: 4,739

    I just clicked on it, beleive it automatically came up in windows media player.

    Seth, here's a thought... if you think it is something major, its probably better to just replace the engine for $254.99 ( than to take it to a shop. In just an hour the shop charge will likely be at least $50 plus parts and tax, and even if they fix it, it is still a used, worn engine. Don't count on that they could do it in just an hour either.
  7. sethsodsquad

    sethsodsquad LawnSite Member
    Messages: 182

    I kinda would like to know what is causing the noise though, so if I could, I could fix it. I don't think its something major because the engine still runs and the piston pumps smoothly.

    Btw, it's not my main mower anyways, so its not a huuuuuge issue.

  8. bugspit

    bugspit LawnSite Senior Member
    Messages: 767

    I've got a B&S 6.5 doing the same thing. Something I found but did not completely eliminate the noise was the pull starter casing had only one screw holding it securely. 3 of 4 had vibrated out.

    But again, a knocking still exsist at start up and shut down. I wonder what kinda of oil pump these have and if it's not the rod knocking due to lack of oil??

    Mine also runs great, blows a little oil at start up but fine otherwise.
  9. PLM-1

    PLM-1 LawnSite Bronze Member
    Messages: 1,640

    this may be far fetched and totally not the problem but have you cleaned out the intake on the top of the engine. i had an engine that had a similar problem. there was a small piece of wood stuck in the intake recoil area and it was jammed in there and making noise. i only heard it on startup and shut down. i figured that was when the engine was the quietest and it was just easier to hear. you never could be as simple as that! Good Luck!
  10. PLM-1

    PLM-1 LawnSite Bronze Member
    Messages: 1,640

    now that i have listed to it several more does sound more metal on metal! Scratch my previous post!!!

    but then it sorta sounds like partially clogged exhaust

    i dunno...

    let us know what it was when you find out

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