I have a Sears riding mower with a 17hp intek 311707. Engine keeps shearing flywheel key. I replaced 1 sheared key and it started and ran well. Next time I tried to start it, I found the key had sheared again. I replaced the key again and tried to start. 1st attempt sputtered and sheared the key again. I am running out of flywheel keys (and patience). I have adjusted valves and cleaned carb, replaced air and fuel filters. I don't have a torque spec for flywheel bolt, but I am certainly tightening it. Any ideas?

Thank you

How did you adjust the valves? I BELIEVE, you put the piston 1/4" down on the power stoke and adjust both valves to spec.

Intake to .004 and exhaust to.006. Piston 1/4" atdc. Engine cold. Seems to be SOP from all the info I get from these sites

Remember that tdc occurs at 2 places, after compression and at the power stroke. You want the piston to be 1/4" down in the cylinder just at the power stroke.

intake - intake valve open
compression - both valves shut (1/4)
Power - both valves shut (1/4) *
Exhaust - exhaust valve open

You want the * for the 1/4" measurement. e.g. when the piston starts to go down.