Blade won't turn on push mower after hitting stump

JoeinClemmonsApril 24, 2011

Hello Everyone,

I was mowing my lawn with a gas powered push mower and it hit a small, hidden stump. The mower immediately went dead. I tried the pull cord and it wouldn't budge. I turned the mower on its side and tried to move the blade by hand. The blade was difficult to move. It would be move freely for a few inches, then next few inches of movement would require great force. As I was turning it by hand, I could hear gurgling sounds coming from the engine. Also, as I lifted the machine back upright, I saw that oil had leaked out onto the ground through the muffler guard. (This mower was in great shape before it hit the stump. It was purchased new and was only on it's third mowing). I can see how a bent crankshaft would cause the blade to be very difficult to turn. Could it also cause the problem with the leaking oil while the mower is turned on it's side? I have turned it on it's side in the past and nothing has leaked out. I know that it does not look good for this mower at this point. Any ideas would be appreciated. Thanks, Joe

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You caused the oil leak by tilting it up with the carburetor side down, which you should never do. Sometimes oil is sucked into the cylinder and results in a hydraulic lock. Take the spark plug and air filter out. If it's a pleated-paper filter, you'll need to get a new one if the mower can be used again. Pull the starter cord with the plug out to get a feel for the severity of the problem and to clear the oil from the combustion chamber. Now you can tilt it up with the carb side high to check for a bent crankshaft. Spin the blade to see if the blade bolt head seems to describe a small circle rather than just turning in place. The other problem usually resulting from an accident like this is the flywheel probably sheared off the key and tuned on the shaft. You'll most likely have to reset the flywheel before it will run. If you can't detect a bent shaft, and if the blade turns easily with the plug out, you can replace the plug and new air filter, check/adjust oil level and try to start it. If it kicks back and backfires, etc., you'll have to reset the flywheel with a new 'Woodruff key'.

    Bookmark   April 24, 2011 at 3:58PM
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Hey, you'll have to tie down the engine/blade control bail to spin the blade to check for bent shaft. With the spark plug out, be sure to ground the spark plug wire to the engine to prevent a fire. Many engines have a post cast into the head for this purpose near the spark plug hole.

    Bookmark   April 24, 2011 at 4:02PM
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Yeah I agree with Sax . Although you may indeed have bent the crank . As recommended examine the blade rotation and locate the high spot . Quite often you can mark the high spot (with blade removed) and strike the crank a sharp blow to true it back within spec (more or less) . Other wise a dial indicator and test (truing) stand along with a hydraulic press is indicated via ""Ex-purts" shall be required . Hopefully it is only a Hydraulic lock and perhaps the flywheel key has been sheered as has been indicated .

    Bookmark   April 25, 2011 at 9:57AM
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You may have a bent blade or a bent crankshaft. Or both. And as indicated the key may have been sheared. Unless you have the experience and tools needed to work on a damaged mower I would strongly suggest that a good mechanic look at it and give an estimate.

    Bookmark   April 26, 2011 at 1:58PM
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Sounds like you have just made yerself an expensive "boat anchor!" But, check it as described above, but don't expect miracles! Then go buy an axe, or a "pick-mattock. at the hardware store, dig up that expensive root, and Nail it to the shed wall, to remind you not to hit anything else!
A twisted crank-shaft is relatively impossible to fix, as is a bent one!

    Bookmark   April 26, 2011 at 6:16PM
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