1989 45hp what makes a stator go bad?

[dkonrai]

i bought this motor, off cl. had no spark so i changed the stator and now it runs! question, what makes a stator go bad?

here is the motor running.

https://www.youtube.com/watch?v=zf9yIpWkPS8&feature=g-upl&context=G216840eAUAAAAAAAAAA

old stator

dino