Did it overheat? Did you lose coolant or maybe the fans didn't kick on? Maybe it seized?

Funnyman may be onto something too.

what is the key for the flywheel.

And I dont think it overheated. It was a short drive and never went over 3/4th throttle

Its something that keeps the flywheel at a certain position on the crank which times the spark a the right time.I know its the condensed version, but it could be your problem.

When you pulled the flywheel to change the stator, you should have seen the key in the crank. Is it possible it fell out and you have no key?

uh oh It makes good since