Small Engines (Lawn Mowers, etc.): flywheel key keeps breaking on start., briggs and stratton, air gap

Question
a friend gave me his old craftsman 17inch rototiller( partnumber 917.29969). everytime you start it, it cranks over and the breaks the flywheel key. this happens with no belts or load aplied to the motor. we pulled the flywheel off and re-keyed it and put it back on. then we turned it by hand and found that 1 small area of the flywheel was hitting the magneto. it is only about an inch or less of the flywheel that touches but we moved the mag up to clear it and it still broke the key. what could cause this? i keep hearing that the valves could cause this but they look ok but have not changed them yet. any input would be great. by the way the engine is briggs and stratton model is 130202 type 3129 01. thanks again.

Answer
 Hello Rick:

 I have Never Seen the Valves Cause the Flywheel Key to Shear. Are you Torquing the Flywheel Down to 150ft Pounds? If yes, then Increase the Torque by 10ft Pounds Until the Flywheel Stays Tight on the Crankshaft. Set the Coil to .020in Air GAp from the CLosest Point the Coil and Flywheel Meet. You can View a Breakdown/IPL of the Engine at this Addy http://www.outdoordistributors.com/ and Select the B. Then Select Briggs and Stratton. Then Select Don't have Part Numbers. Then Select the File Number 13. Then Select the Folder # 130200. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John