Hello all, Friday, buddy and I went trail riding and rode fine for about an hour. Went back to the trailer to grab some water and bike wouldn't kick back over. Its a 2001 426 stock bike. Piston and rings are 2 years old. Seems like I've lost compression. I tried pulling the spark plug and it was really hard to get out. After I got it out, it looked like it took some of the threads with it. Was going to break it down today to try and find the culprit, but haven't decided where to start. I'm thinking valve clearances?