flywheel key sheered any idea why?

[Daddyof4]

My woodruff key was missing from a parts bike which I thought was strange so I rebuilt the engine and put a brand new key in and started the bike for about 2-3 seconds and it sheered it. what would cause it to sheer? any help would be appreciated. I can buy another key but I don't want to keep buying them at $10 a pc

 

[bummer981]

The key simply holds the flywheel in place. It is used for timing only. What keeps it from spinning and shearing the key is the taper and correct torque on the nut. The flywheel must be lapped to the the crank with lapping compound to assure proper fit.

 

[Blaaster]

Same process.

 

[Daddyof4]

Same process.

Thanks for the advice. Do you know what the torque is on the flywheel?

 

[Daddyof4]

My woodruff key was missing from a parts bike which I thought was strange so I rebuilt the engine and put a brand new key in and started the bike for about 2-3 seconds and it sheered it. what would cause it to sheer? any help would be appreciated. I can buy another key but I don't want to keep buying them at $10 a pc

Do you know the torque of the flywheel?

 

[Blaaster]

53ft lbs, dry no Loctite

 

[Jimmer]

Twisted crank with big runout?