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rsnik

Shearing flywheel key

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rsnik
The 717 lost spark. New plug, new points. No joy. Take it down again (I can get to the flywheel off stage in about 5 minutes now) and whoops! the flywheel key is sheared off. Go down and buy a bunch of flywheel keys. Change out the key, put it back together and it starts instantly and runs for 5 seconds and quits. I deconstruct back to flywheel off (5 minutes) and the key is sheared off again. Any idea why this is happening? Best, rsnik

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HubbardRA
As Maynard said. The key is just for alignment purposes. It is the torque of the nut pulling the flywheel up on the taper that holds the flywheel in place, and prevents it from turning. The key should see no load once the flywheel nut is torqued properly.

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ZippoVarga
I had a similar problem with a small horizontal briggs. Turned out that no matter how tight the nut, I was spinning the flywheel. Wound up being an oil seal that had efectively glazed the tapered shaft and made it slicker than Ice. I took the crank and just lightly touched it with 600 grit emery paper and brass brushed the flywheel after replacing the oil seal. This cured the issue and that engine has never had another key issue. Just a thought and a possible cause via my past experiences. I would check the oil seals just in case. Sean

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Al
Hi, Make sure the "Belleville" washer is on the right way up. The dished side it up in the center and the outer edge bears down on the flywheel. If they are turned over you can't hold a key. Al Eden The same problem occurs if the cupped washer under the bolt is flipped over on the blades on the newer mowers with the splined shafts and 1 bolt blades. The blades will slip and it will break the washer with the internal spline

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rsnik
Thank you, thank you, thank you! Did not want to go borrow the puller again so did lots of gentle prying at the keyway and shocking the flywheel with a dead blow hammer (with a sheared pin she's a little shy). Finally popped off. Back together again and properly torqued with the new carb and points and all and she runs like a red tape! This is the 717. I bought that 728 that had just come back from the dealer with a new carb and points, new tires and a rebuilt deck and threw a rod. The 728 is now a pretty stripped donor. Put all the tin back on the 717 along with the new rear weight (bless you alistractorman) and the new deck and went off to mow my acre. Man, that Simplicity deck (granted it is all rebuilt with new blades) cuts so crisp it is just shocking compared to my Murray. The lawn got high as I have been working every spare moment on the tractors and even robust, heavy, thick lawn gets buzz cut right down to the ground if you like without stressing or bogging the unit. Then, when all done, I just drop the deck in 2 minutes and power wash it clean and snap it back on. Suffice to say I am a happy camper. Thanks all for the flywheel key fix, thanks mowerman for the carb advice and, well, thank you, thank you, thank you! Best, rsnik

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