How can I fix my dirtbike?

Here is whats up. I was riding at my friends house one day and it just died out of nowhere, even worse, the kickstarter was jammed. We took it back to his house and had his dad look at it because he is a mechanic and he got the kickstarter unjammed but it still wouldn't start. That was two years ago and it still won't start, i have already tried changing the spark plug ans that didn't work. I don't know if this helps but it is a Kawasaki KX65, i am not sure what year it is.