Recently, I submitted a post on here regarding a broken ground electrode on the spark plug of my 2005 Suzuki RM125:
Well, I found out what caused this. The piston is traveling too high in the cylinder and actually running into the spark plug. After riding with a new plug (NGK BR9ES), I took it out and noticed that the ground electrode had been bent all the way to the center:
What could be causing my piston to travel so high and slam into the spark plug? My best guess is something in the bottom end (crank, rods, etc.) is worn or out of place. Am I going to have to replace the entire bottom end? Or maybe just the crank bearings. Any ideas?