Lawn mower engine knock

Discussion in 'Other Repairs' started by olefin, Nov 22, 2009.

  1. olefin

    olefin New Member

    Messages:
    3,908
    State:
    Texas
    I was mowing leaves in an area where I normally don't mow and hit a rock sticking out of the ground. The impact kill the motor! It restarted ok but had a bad knock. Went ahead and finished grinding up leaves. Later removed plug wire, pull the starter, could very well hear the engine knock. Checked under the mower, nothing was hitting the blade, also turn blade by hand to be sure it was free.

    Few days later mowed the yard, motor was still knocking. Wife said she could hear it from inside the house. Was almost through and suddenly the knock got much worse, sounded like the piston was coming through the head and then the motor died. But on first pull it fired right off, the knock is gone and the engine runs ok?

    I don't understand it. :confused2:
    Someone want to explain what happen?

    I hit a stump with another mower few years back, also kill the motor but it wouldn't restart. Found the crankshaft pin was sheared on the flywheel. I replaced pin and motor was ok.
     
  2. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Yea I am wanting to hear this one. It could have been the oil slinger or it knocked the blade out of the notches and it went back into place. Most time when they do that dayton you most times have a bent crank. Run Her till she drops.:wink:
     

  3. coonboydan

    coonboydan New Member

    Messages:
    4
    State:
    north carolina
    You probably broke carbon loose on top of piston,this will cause it to hit the head,then later it just went out the exhaust. Coonboydan
     
  4. Fl.catman

    Fl.catman New Member

    Messages:
    132
    State:
    Fl
    If it is a B & S. They will do that if you have a stuck valve that is opening only half way. it may have jammed when you hit the rock and broke loss later.
     
  5. olefin

    olefin New Member

    Messages:
    3,908
    State:
    Texas
    Willard, gave that some though but how would that make the engine knock? Did notice when I removed the blade to sharpen, that the bolt was hard to break free? Had to use a cheater and never before in my life needed a cheater to remove a blade bolt.
     
  6. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Dayton if it had nocked it out of place the engine would have viberated a whole lot to and it would be noticeable when you took the blade off. I am guessing But I will go with the theory of the oil slinger. If it had bent a rod or crank you wouldn't have been able to hold it still and it would not have went away. There is a key way right under the attatchment for the blade now it could have slipped half way and it does have a 1/4 key stock on it.
     
  7. catfisherman369

    catfisherman369 Floyd

    Messages:
    4,944
    State:
    Nashville Il.
    My 18 horse briggs done the same crap a few weeks back , and I never hit anything . Knocked the whole time I used it . About a week later I started it up and the knock was gone . Hasnt knocked since .
     
  8. olefin

    olefin New Member

    Messages:
    3,908
    State:
    Texas
    Willard, didn't notice anymore vibration than normal. When I removed the blade I checked the key on the blade attachment, was in place and looked ok. Your oil slinger theory sounds closer than anything.

    Sounds like I'm not the only one that's having Gremlins.:big_smile:
     
  9. Fl.catman

    Fl.catman New Member

    Messages:
    132
    State:
    Fl
    The bolt will tighten if you hit something like a rock. The harder the impact the tighter the bolt will get.
     
  10. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    I love a good mystery though.:wink:
     
  11. 223reload

    223reload New Member

    Messages:
    10,798
    State:
    Oklahoma
    Strange indeed,I killed a murrey rider last fall,mowing away,when the rod cap bolts fell out,found that out when I took it apart. Factory defect I guess.
     
  12. smokey869

    smokey869 New Member

    Messages:
    966
    State:
    frederickt
    the only thing i can think of is the carbon, only thing that would or could go away and not leave a trace that you could easily see, hmm a real head scratcher there, if its running ok just run it, i bent the crank on one it shook so bad the gas cap came off after about 20 feet when i tried to finish, i bet i looked like one of them cartoon guys hooked up electricity lol
     
  13. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Love my Yazooooooo!
     
  14. mikey823

    mikey823 Member

    Messages:
    95
    State:
    Illinois
    I love my W. Horse.
     
  15. Catfishboy1995

    Catfishboy1995 New Member

    Messages:
    3,104
    State:
    Council Bluffs
    well i have pocket midgets you must have just midgets thet mess with every thing...lmao...i came up with pocket one day i was a school and weight to my weight lifting class and pulled yout my Ipod and a pencil went all the way through my head phones...i have no clue how it happened and my phone calls people all the time..lmao!!!
     
  16. Catfishboy1995

    Catfishboy1995 New Member

    Messages:
    3,104
    State:
    Council Bluffs
    i gotta cub cadet that is a work horse...i think a johndeere would be better though!!!