shearing fly wheel keys

[vf24tomcat]

I have a brigs 21 hp moter on my rider. wife was riding it and went over a bump came up off seat, moter backfired and started poping. found flywheel key had sheared. replaced key went to start up and it woundn't start,poped again. took apart and key was sheared again and flywheel was cracked. replaced flywheel and key. tried starting before i put covers back on, started up and ran great, let it run for 5 min turned off and put covers back on and tried to start. fired for a second then quit then would not start. checked flywheel and key was sheared again. need some help on this on

 

[ILENGINE]

Make sure that all the oil and grease residue is removed from the crankshaft taper and the taper in the flywheel. then make sure the flywheel bolt/nut is torqued to spec.

Most common problem on rider engines shearing flywheel keys is improper torque.

 

[vf24tomcat]

cleaned up all parts and put back together and torque to100 lbs and sheared another key. I then stared over and torque fly wheel down befor installing fan and metal top. I then took out bolt and installed fan and cover and retorqued bolt to flywheel. works great