I bought a used 06 450F and after comparing it to my brothers bike it was much noisier with the low speed clinking noise. So this afternoon, I removed the head and cylinder thinking it may be the big end of the rod. It's all tight... no apparent crank problems. The webbing at the big end of the rod is discolored but nothing is loose. Is the discoloration a problem? I know the bike was raced hard in the past. How do I know if it needs a piston? It ran fine and the cylinder and piston look fine. Should I put a piston in it if it has been raced and has over 50 hours on it? What are the signs? Is it the same as a two stroke where it would show physical wear cause it really shows nothing.