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OT..Lawn Mower Engine Help

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  • OT..Lawn Mower Engine Help

    In the hopes of clearing some floorspace this winter, I hung my Toro lawn mower on the wall. That was a couple weeks ago and this weekend noticed oil on the floor. Looks like it came out the muffler. I got it down and disconnected the plug wire to turn it over. Went about halfway and locked up. Pulled the spark plug and motor spat a bunch of oil out the the spark plug hole. So it looks like the cylinder has a bunch of oil in it. How do I get it cleaned out? It's been almost thirty years since I had a small engine apart so I don't remember what all is in there and I don't fancy tearing it apart. I was thinking about soaking as much as I could with towels and then rinsing it out with gas/thinner/alcohol and compressed air. Is there a better way?

  • #2
    Since your only dealing with oil from the crankcase seeping past the rings and no appearent damage, just pull the spark plug and crank the engine over. It'll spew the excess oil out of the cylinder. Then pour a bit
    of fuel into the cylinder and do it again to help clean out any remaining oil. (make sure there's no smoking and the spark plug wire is securely grounded!)
    put a new spark plug back in and start up the mower. Be sure to drain and replace the oil in the crankcase just in case you may have gotten some fuel in the crankcase. You'll probably want to get two new spark plugs as the one you use for the initial startup may become oil fouled.
    Last edited by Scottike; 12-19-2011, 12:47 PM.
    I cut it twice, and it's still too short!


    • #3
      Drain the old gas in the tank and the oil out of sump, then drain the balance out though the spark plug hole. Leave it draining for a while, pull over a few times when upside down.

      Refill the sump, gas it up, clean or new plug and start it. It will smoke for a while, and may foul the plug a couple of times, but it will clear.

      And... store it level!


      • #4
        Don't rinse it out with thinner or solvent. It may damage some parts. I'm not sure about Toro but Briggs uses acetal camshaft lobes. Acetals are very resistant to nearly all petroleum products and most solvents but there are some oddball exceptions. Isoporopy alcohol, grease and lacquer thinner will all attack acetal strongly.
        Free software for calculating bolt circles and similar: Click Here


        • #5
          All of the above are good advice. Most likely after draining or pumping out as much as you can with engine sans spark plug you will be able to start it after a few pulls with no damage. It may smoke for a few minutes but that will clear. Do be certain to check your crankcase oil level before starting though. Whatever drained into the cylinder head needs to be replaced before starting. You may want to check the plug after running it for a few minutes to see if it need cleaning but most likely it will clean itself over time if the engine isn't badly worn and doesn't consume enough oil to smoke.

          Instead of using a solvent to "wash" the oil from the cylinder you might be able to use a thinner oil like Marvel Mystery Oil to "rinse" it out. Pour some through the spark plug hole, slowly pull the engine over with the plug to mix it up a bit then tip it over and allow to drain. If any Marvel Mystery oil makes it to the crankcase past the rings no worries. It is designed to be mixed with both fuel and motor oil and has detergent properties to clean up engine parts. MM Oil is a "snake oil" that I personally believe in.

          I doubt you will need to drain the fuel unless you need to to tip the engine to a position to remove the oil from the cylinder. Most likely the oil got there because the cylinder/head was inverted and oil ran past the rings or valve guides. Most B&S engines I've seen have the carburetor in a position that would be higher than the cylinder/head if the engine were inverted, assuming you aren't talking about a V Twin Vanguard or OHV engine. I am not that familiar with those models.

          If you must store the mower vertically on the wall just be certain the cylinder head is pointing up. The oil should remain harmlessly in the crankcase as it imitates a horizontal shaft engine in that position.
          Last edited by firbikrhd1; 12-19-2011, 03:02 PM.


          • #6
            Drain the oil/fuel from the engine/crankcase. Existing crankcase oil may have fuel in it, is likey time to be changed anyway, and is missing some.

            remove the sparkplug and violently pull start it after tilting the lawnmower with the plug hole 'down' and drain as much oil via action of the piston cleaning the cylinder, Then just put sparkplug back in, add fuel to the tank, oil to the crankcase and run normaly.

            The left over oil in the cylinder won't hurt it, as long as theres not so much that it hydrolocks the piston. (Aka, enough to fill the cylinder with the pistol at top dead center.) or greatly incresses the compression (Aka, a good deal of oil, More then will be left after letting it drip out for a minute with the engine tiped over)

            Do NOT try and clean the last of the oil out with solvent. Why on earth would you want a cylinder with no lubrication?!?

            One of my tricks when storing a motor was to pour a tablespoon of oil down the sparkplug hole, crank the motor over a few times to coat the cylinder nicely, then put the sparkplug back in with the cylinder at top dead center, Keeps the combustion chamber from rusting. Better yet is pull it untill you can feel your on the top of the compression stroke, so you know your valves are shut too. (Only for 1 cylinder motors of course..)

            Never bothered to empty any of the oil from the cylinders before starting. Had some lawnmowers that would burn oil badly when you filled the crankcase up too much (Apparently too much is the 'fill to' line on that lawnmower..), They just blew tons of smoke untill they stoped burning oil.

            Oil in the cylinder AFAIK is not a bad thing at all, Except for the fact it might foul your plugs over time (More likey it will just smoke like mad for the first few minutes then run fine, fouled plugs just need a good cleaning and just stop the motor from running till they are cleaned)
            Last edited by Black_Moons; 12-19-2011, 03:07 PM.
            Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


            • #7
              Most of your common garden variety lawn mowers are powered by a Briggs & Stratton, Four-stroke , side valve engine. Kinda like working on 1/8 of a Ford flathead engine, only more powerful.

              I think the only ones you can just hang up on the wall are the electric ones.
              No good deed goes unpunished.


              • #8
                Just take the thing off the wall and start it up . Once it blows the oil out it will stop smoking and be fine . not need to take any thing apart pull the plug and give it a few spins put plug back in and it will run ok. Been their done that . Every season no worry.
                Every Mans Work Is A Portrait of Him Self


                • #9
                  Best lawn mower I ever had was a 2 cycle Toro.
                  When I moved back to Ala from Omaha, I rented a small house for a while until I found a job and bought a home. Stored mower under the crawl space and then had biblical floods for a week or so, during which time the mower was totally submerged.

                  Poured the water out, disassembled and cleaned the carb, put fresh gas in and it started on the first pull, just as it always had.

                  They probably don't make the 2 cycles any more.

                  I doubt that flushing is needed for the OP's mower, but if I were going to do it I'd probably use diesel fuel or something along those lines. It should provide some lubrication until oil can coat everything during the first few seconds of operation.
                  Lynn (Huntsville, AL)


                  • #10
                    I would hang it back up with either a drip pan or some rags underneath to catch the oil. In the spring, as others have suggested, drain the crankcase and give it a few good pulls without the plug in, then start it as usual.
                    "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."


                    • #11
                      Originally posted by lane
                      Just take the thing off the wall and start it up . Once it blows the oil out it will stop smoking and be fine . not need to take any thing apart pull the plug and give it a few spins put plug back in and it will run ok. Been their done that . Every season no worry.
                      Yeah, I tried that. The plug fouls immediately because of the excess oil in the head. I'll drain the sump, was going to change the oil in the spring anyway, and then prop it up with the plug out and let gravity due the work for me. Thanks all.


                      • #12
                        Spark plug

                        Try to find AC plugs for your mower. The Champion ones don't last very long, especially in an oily environment (typically 2 stroke). An AC plug will outlast several Champions. At least that's been my experience.
                        Kansas City area