The key on the flywheel must have sheered. The magnets on the flywheel are not passing by the magneto at the right time to send the spark to the sparkplug. That is the timimg. To repair, the flywheel must be removed and inspected for damage and a new flywheel key must be installed and the flywheel nut must be torqued down to the proper spec's.
JOHN
September 2004