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Helpful ReplyHot!Flywheel Key keeps shearing !

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jmf111361
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2017/08/25 16:58:21 (permalink)
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Flywheel Key keeps shearing !

I have a Craftsman LT 4000 18.5 hp Briggs & Stratton engine. What (besides hitting something with the blades) would make the key shear within minutes of replacing it ? I just changed the oil & filter, it crunch right up and within no time it shears the key !!!???  Any idea's ?? 
Mikel1
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Re: Flywheel Key keeps shearing ! 2017/08/25 17:44:43 (permalink)
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Are you properly torquing the flywheel?
AVB
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Re: Flywheel Key keeps shearing ! 2017/08/25 17:56:46 (permalink)
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Need the model, type number and date code. Some Briggs have since been upgraded to steel keys and increase torque specs.
jmf111361
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Re: Flywheel Key keeps shearing ! 2017/08/25 18:15:13 (permalink)
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I'm not sure of the torque spec's but I had it pretty tight. When I took it back apart the main nut was not tight ! I was surprised ! Someone else today said something about me making a steel key. You think that would hurt anything ?
jmf111361
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Re: Flywheel Key keeps shearing ! 2017/08/25 18:55:01 (permalink)
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Thanks AVB.
Model # 31P777
Type  0348 E1
Date  040225ZE
AVB
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Re: Flywheel Key keeps shearing ! 2017/08/25 21:20:54 (permalink) ☄ Helpfulby amkaplan 2020/08/20 02:37:30
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Okay your engine was subject of APSI 82 Bulletin back in February 2012 about flywheel key shearing. Briggs redesign the crankshaft and flywheel on July 1, 2012. (ASPI 89). Your engine is a 2004.
 
Order flywheel key PN 796335. This is a steel key. Also increase the flywheel nut or bolt to 110 ft-lbs old spec was 100 ft-lbs. Use a torque wrench to tighten; no guessing or the use of impact wrench (a NO-NO). If not done to spec flywheel and crankshaft damage can occur.
 
Your automotive parts store should have loaner tools if you don't have a torque wrench or go to Harbor Freight they are on sale right now around $10.
post edited by AVB - 2017/08/25 23:06:31
jmf111361
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Re: Flywheel Key keeps shearing ! 2017/08/26 10:18:38 (permalink)
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Thank You so Much AVB !!!
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Re: Flywheel Key keeps shearing ! 2018/11/26 09:56:10 (permalink)
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Did the steel key work?
jmf111361
Thank You so Much AVB !!!




AVB
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Re: Flywheel Key keeps shearing ! 2018/11/26 10:15:55 (permalink) ☄ Helpfulby amkaplan 2020/08/20 02:37:45
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Should have since it been over an year since the last post.
 
BTW this only applies to 280000, 310000, and 330000 prior to 07-01-2012 (date code 120701****). Briggs redesigned the flywheel and crankshaft and are using double length aluminum key on the new engines. Don't use the steel key on the newer engines.
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Re: Flywheel Key keeps shearing ! 2018/11/26 14:05:10 (permalink)
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Thank you.  Mine is a 310000 series manufactured 03-31-2011.  I'll post what I find.
AVB
Should have since it been over an year since the last post.
 
BTW this only applies to 280000, 310000, and 330000 prior to 07-01-2012 (date code 120701****). Briggs redesigned the flywheel and crankshaft and are using double length aluminum key on the new engines. Don't use the steel key on the newer engines.




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Re: Flywheel Key keeps shearing ! 2020/08/20 02:40:18 (permalink)
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AVB
 
BTW this only applies to 280000, 310000, and 330000 prior to 07-01-2012 (date code 120701****). Briggs redesigned the flywheel and crankshaft and are using double length aluminum key on the new engines. Don't use the steel key on the newer engines.



Very helpful comments above.  I am shearing keys and nothing unusual is happening to cause the problem, just mowing grass.  Once I pull the flywheel, I'll check the surfaces, etc, but was hoping to find out more about a new key.  The motor is a 31C7770226E1, 040103ZE68555.  From what I read, it sounds like the second number is a date code, but I have no clue as how to translate it.  At points you mentioned a steel key #796335 and longer aluminum one; can you direct toward the correct key, and give me any more tips on how to keep the keys from shearing?  One suggestion was using a washer under the bolt - it's easy to find one, if you think that will make a difference.  BTW, you mention NOT to use an impact driver, but this is what the shop I went to uses; could you please explain?  I'm happy to use a torque wrench instead.
 
This has been a major pain in the butt, and I just want to mow my grass!
 
Many thanks,
 
Allan
 
 
 
AVB
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Re: Flywheel Key keeps shearing ! 2020/08/20 07:07:22 (permalink) ☄ Helpfulby amkaplan 2020/08/20 12:53:47
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I received a notice that there was a new post to this old thread.
 
I just to make a correct about the longer key. It is a Steel Long Key 1-5/64" (PN 591757) and not aluminum as I since since 2018 have ordered in the long key here.
 
 
post edited by AVB - 2020/08/20 07:10:48
AVB
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Re: Flywheel Key keeps shearing ! 2020/08/20 08:23:57 (permalink) ☄ Helpfulby amkaplan 2020/08/20 12:53:41
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amkaplan
BTW, you mention NOT to use an impact driver, but this is what the shop I went to uses; could you please explain?  I'm happy to use a torque wrench instead.
 
This has been a major pain in the butt, and I just want to mow my grass!
 
Many thanks,
 
Allan

IT because they can either be under torqued allowing the flywheel to slip on taper or over torque leading to either the flywheel being permanently stuck to the taper, the flywheel being lower then the spec height, or even cracking the flywheel leading to a explosive failure.
 
Maybe later today I can get a n image of one the failed because over torquing. It didn't come a part completely but the center is definitely busted so bad the flywheel was left spinning on the crankshaft.
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