Walk Behind Mower Cord Pulls Back

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  #1  
Old 06-05-17, 09:44 AM
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Walk Behind Mower Cord Pulls Back

Hi - I have a Murray 22" self-propelled lawn mower (model 7800465), that has a Briggs & Stratton 650 series engine (124T02-0301-B1). Recently the engine has become harder to start, with the pull cord becoming very hard to pull and even having the cord pull back on me on occasion. When the spark plug is removed, the pull cord/fly wheel spins with no resistance. Once the engine starts running, it runs just fine. My suspicion is that either there is a buildup of pressure in the cylinder that is not being released, or that the fly wheel key is sheared. When I exposed the fly wheel, the attached picture shows what the key looks like. Is it damaged? I wanted to make sure before pulling the fly wheel off.

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If the key is OK, are there any other ideas for the cause of the stiff cord/cord pulling back?
 
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  #2  
Old 06-05-17, 10:59 AM
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Trying to start it with no blade or a very worn out short blade will do this. The engine is dependent on the flyweight of the blade to help it start and keep the momentum going. That's why the flywheel is aluminum in stead of cast iron. On engines without a blade or external flyweight, the flywheel is cast iron to make up for it.
 
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Old 06-05-17, 12:43 PM
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The mower has a proper blade on it (the original blade).
 
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Old 06-05-17, 04:33 PM
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And it has not worn thin or short?
 
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Old 06-05-17, 05:44 PM
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You can't always tell by just looking you need to remove the flywheel the keys can be very deceiving. Have a good one. Geo
 
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Old 06-05-17, 05:44 PM
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And is it balanced? If you sharpened the blade yourself, you should make sure it's balanced.
 
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Old 06-05-17, 06:02 PM
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For those that question my comment about the keys being deceiving check the pics below. Have a good one. Geo

Looks good:



OOps Not ok:
 
  #8  
Old 06-05-17, 06:13 PM
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good one!___________________________________________
 
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