So I was riding my friend's ninja today, and we had to put it away because it was making this ticking noise. When we ran the engine and gave it a little gas it would tick near the top. I did a little searching around on other forums, but I was curious as to what gearheads on this forum would say. What could it be? Maybe timing chain? And is that an expensive/laborious repair? Could I do it myself with or are there any specialty tools needed? Any help is appreciated.