Piston removal?

Discussion in 'Mechanic and Repair' started by mnickison, Jan 15, 2008.

  1. mnickison

    mnickison LawnSite Member
    Messages: 22

    I have a briggs motor thats been blown. The connecting rod is shattered. How do i remove the piston to replace the rod? Thanks much!
  2. MuleCutter

    MuleCutter LawnSite Member
    Messages: 212

    take the engine off and remove head and the crankcase cover. this allows you to get to the connecting rod bolts. once you remove the rod bolts the piston should slide right out the head.
  3. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    If you meant removing the piston from whats left of the shattered rod you didn't post model numbers. But you can use the below as a guide.

  4. Landrus2

    Landrus2 LawnSite Fanatic
    Messages: 5,050

    Want to save your self some headaches go out and buy your self a new motor :hammerhead:

  5. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Joe, This one saves even more headaches.....:waving:

  6. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    I just went through this...

    You'll need more than an outside engine inspection to determine the problem, so if you have some time it takes 1-2 hours to pull it off and apart, since you likely have to pull it anyhow, but plan on replacing it.

    The thing is getting that effing cover off there is a gear that powers the governor that is in the way, and you can't remove the gear so you use a universal gear puller to get that cover off and hope for the best... In my case it broke the e-clip holding the gear (no biggie I have tons of those) and it bent the pin the gear was riding on, I did get it bent back to what looked like straight but turning the gear manually revealed some truly minor drag along a certain part.
    Well, straight pin is as straight as I could get it, I let that be.

    Then the main bearing was a bit rough but some pressurized air and oil and it felt smooth again with also just a tiny bit of drag at some point, you could just barely feel it.

    The piston had cracked, too...
    The crankshaft was damaged also, didn't see that at first, but it made sense because this was what actually caused the connecting rod to snap, it froze onto the shaft...
    See now the ignition / recoil end of the engine has to come off too, by now I was looking at $200 in parts minimum.
    3-4 hours labor, and don't forget the TDC compression bitty when it goes back together.
    Well gee, you know, are those bits of drag really that minor, if I go through all this trouble will it work?

    Because so much collateral and possible collateral damage happens when a rod shatters, I didn't think it was feasible to go through the trouble of rebuilding a blown engine then HOPING it would run.
  7. mnickison

    mnickison LawnSite Member
    Messages: 22

    Thanks guys! I will look up the cost of the 2 new motors i need. Seems like quite a bit to spend when the replacement parts only total about $80 for both motors. I have the engines torn completely apart. Everything looks good except for the connecting rods, but im sure something got stuck, otherwise these rods wouldnt have broken. I dont have the motor numbers on me, theyre back at the shop. Any recommendations on a site for new motors? They are 6.75 hp briggs for push mowers, came off a couple John Deeres. Thanks again.
  8. MarcSmith

    MarcSmith LawnSite Fanatic
    Messages: 7,157

    of the con rod broke, then most likely you've got scoring/transfer on the crank and possible scoring on the cylinder walls. Why did the conrod break? the the bearings seize

    so while part may be only 80 bucks. if you need to have the cylinder honed or the crank turned you could be looking at 100 more dollars for each.....to get a machine shop to clean it up for you.
  9. mnickison

    mnickison LawnSite Member
    Messages: 22

    The mowers were both brand new and the first owners didnt add the oil to them prior to cutting their grass. Needless to say, they were ran without oil. I paid $50 for the mowers and thought i could fix them easily. I'm pretty new to small enginie repair. The parts i thought would be needed are the rings on the piston and the connecting rods. Apparently it may be more than that.
  10. GravelyNut

    GravelyNut LawnSite Bronze Member
    Messages: 1,594

    Depending on how bad the rod siezed on the crank, it might be saveable. It does require chemicals that are best left to an engine shop.

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