flywheel keys keep shearing.

bebuzz69

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i have a 10 horse tecumseh and every time i pull the starter i shear a key.
what would cause this. i spin the cam by hand and everything is free.
 

Rivets

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If the keyway in both the crankshaft and flywheel are good, the main cause for shearing would be not properly torqueing the flywheel nut.
 

bebuzz69

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never heard of that, usually just use impact wrench to tighten.
 

ILENGINE

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oil/grease contamination on the crankshaft/flywheel taper can also contribute to this problem.
 

bertsmobile1

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You have most likely damaged the key ways.
Check them for burrs and if burred take to them with a fine file.
Then a bit of lapping with some fine valve grinding paste till the whole contact faces is a dull grey.

Careless use of an impact wrench will shear the key, they respond much better to a slow tightening
 

SeniorCitizen

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By using a impact you may have cracked the flywheel.
 

Rocky J

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Been awhile sense I worked on a Tecumseh but didn't they have a off set key in them? If so try putting the key the other way next time and try it, it might be timing kick back.
 

ILENGINE

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Been awhile sense I worked on a Tecumseh but didn't they have a off set key in them? If so try putting the key the other way next time and try it, it might be timing kick back.

It is a tapered offset key so will only fit one direction.
 

bebuzz69

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No this has a woodruff key.
 

bebuzz69

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also i pulled off the flywheel and the key did not shear this time, but it has a kickback like its out of time. so i pulled the pan and the crank gear and the other gear line up right on the marks. so iam at a loss as to why it is out of time.
 
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