Blade keeps coming loose

jamcha71

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I have a craftsman push mower model # 977.377240 that the blade keeps coming loose. I have cranked the blade down as tight as I can and after trying to pull start it the engine won't turn over and the blade comes loose again. Any help would be greatly appreciated.
 

Lawnranger

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Why won't the engine turn over when you pull the starter cord? As you know, the engine should rotate (turn over) and fire (start & run) when you pull on the starter cord. The blade coming loose is a whole separate issue but it needs to be addressed as well.

Did you wedge a short length of 2"X4" between the blade & deck when you tightened the blade bolt?

Did you use a torque wrench and measure how much torque you applied to the blade bolt? The amount of force you applied to the blade bolt could be more or less than I can apply so that is only relative when you say you cranked the blade down tight.

Does the mower have a blade adapter? If so, is the adapter damaged? Is there a washer missing? There could be a lot of reasons for the loose blade problem so some more information would help us help you.
 

reynoldston

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I have cranked the blade down as tight as I can and after trying to pull start it the engine won't turn over and the blade comes loose again. Any help would be greatly appreciated.



For some reason I don't make any sense of what you are saying??? If the blade is coming loose there has to be a reason and one of them would be you aren't tightening the blade properly. And just why would the blade be coming loose if you can't start the mower? There just has to be more to this story.
 

Rivets

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Are you sure that the blade adapter is installed properly? If you don't have the key in the slot or the key is broken the blade will come loose. Some adapters have the key built into the adapter.
 

twinfords

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Are you sure that the blade adapter is installed properly? If you don't have the key in the slot or the key is broken the blade will come loose. Some adapters have the key built into the adapter.

I am with Rivets on this, damaged or faulty blade adapter installation, also the fly wheel key could be sheared causing the mower to kick back.
 

chance123

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This sounds like the adaptor, when tightened, is contacting the base plate under the deck. The Toros have a spacer inside the blade hub for this reason. Did you switch blade hubs? The only time I've ever seen a blade consistantly come loose is when a mower hits a brick, sprinkler head or something else solid. This shears the soft aluminum flywheel key. Then after installing a new blade, then attempting to start, and because the sheared flywheel key offsets the timing, the engine fires backwards which is oppisite the blade/hub/bolt threads, and essentually unscrews the blade bolt with a shock like that of an impact gun. This soft flywheel key is "made" to shear to prevent major damage to the engine in the event of striking something solid.
 
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